Abstract
Background
Postal and electronic questionnaires are widely used for data collection in epidemiological studies but non‐response reduces the effective sample size and can introduce bias. Finding ways to increase response to postal and electronic questionnaires would improve the quality of health research.
Objectives
To identify effective strategies to increase response to postal and electronic questionnaires.
Search methods
We searched 14 electronic databases to February 2008 and manually searched the reference lists of relevant trials and reviews, and all issues of two journals. We contacted the authors of all trials or reviews to ask about unpublished trials. Where necessary, we also contacted authors to confirm methods of allocation used and to clarify results presented. We assessed the eligibility of each trial using pre‐defined criteria.
Selection criteria
Randomised controlled trials of methods to increase response to postal or electronic questionnaires.
Data collection and analysis
We extracted data on the trial participants, the intervention, the number randomised to intervention and comparison groups and allocation concealment. For each strategy, we estimated pooled odds ratios (OR) and 95% confidence intervals (CI) in a random‐effects model. We assessed evidence for selection bias using Egger's weighted regression method and Begg's rank correlation test and funnel plot. We assessed heterogeneity among trial odds ratios using a Chi2 test and the degree of inconsistency between trial results was quantified using the I2 statistic.
Main results
Postal
We found 481 eligible trials. The trials evaluated 110 different ways of increasing response to postal questionnaires. We found substantial heterogeneity among trial results in half of the strategies. The odds of response were at least doubled using monetary incentives (odds ratio 1.87; 95% CI 1.73 to 2.04; heterogeneity P < 0.00001, I2 = 84%), recorded delivery (1.76; 95% CI 1.43 to 2.18; P = 0.0001, I2 = 71%), a teaser on the envelope ‐ e.g. a comment suggesting to participants that they may benefit if they open it (3.08; 95% CI 1.27 to 7.44) and a more interesting questionnaire topic (2.00; 95% CI 1.32 to 3.04; P = 0.06, I2 = 80%). The odds of response were substantially higher with pre‐notification (1.45; 95% CI 1.29 to 1.63; P < 0.00001, I2 = 89%), follow‐up contact (1.35; 95% CI 1.18 to 1.55; P < 0.00001, I2 = 76%), unconditional incentives (1.61; 1.36 to 1.89; P < 0.00001, I2 = 88%), shorter questionnaires (1.64; 95% CI 1.43 to 1.87; P < 0.00001, I2 = 91%), providing a second copy of the questionnaire at follow up (1.46; 95% CI 1.13 to 1.90; P < 0.00001, I2 = 82%), mentioning an obligation to respond (1.61; 95% CI 1.16 to 2.22; P = 0.98, I2 = 0%) and university sponsorship (1.32; 95% CI 1.13 to 1.54; P < 0.00001, I2 = 83%). The odds of response were also increased with non‐monetary incentives (1.15; 95% CI 1.08 to 1.22; P < 0.00001, I2 = 79%), personalised questionnaires (1.14; 95% CI 1.07 to 1.22; P < 0.00001, I2 = 63%), use of hand‐written addresses (1.25; 95% CI 1.08 to 1.45; P = 0.32, I2 = 14%), use of stamped return envelopes as opposed to franked return envelopes (1.24; 95% CI 1.14 to 1.35; P < 0.00001, I2 = 69%), an assurance of confidentiality (1.33; 95% CI 1.24 to 1.42) and first class outward mailing (1.11; 95% CI 1.02 to 1.21; P = 0.78, I2 = 0%). The odds of response were reduced when the questionnaire included questions of a sensitive nature (0.94; 95% CI 0.88 to 1.00; P = 0.51, I2 = 0%).
Electronic
We found 32 eligible trials. The trials evaluated 27 different ways of increasing response to electronic questionnaires. We found substantial heterogeneity among trial results in half of the strategies. The odds of response were increased by more than a half using non‐monetary incentives (1.72; 95% CI 1.09 to 2.72; heterogeneity P < 0.00001, I2 = 95%), shorter e‐questionnaires (1.73; 1.40 to 2.13; P = 0.08, I2 = 68%), including a statement that others had responded (1.52; 95% CI 1.36 to 1.70), and a more interesting topic (1.85; 95% CI 1.52 to 2.26). The odds of response increased by a third using a lottery with immediate notification of results (1.37; 95% CI 1.13 to 1.65), an offer of survey results (1.36; 95% CI 1.15 to 1.61), and using a white background (1.31; 95% CI 1.10 to 1.56). The odds of response were also increased with personalised e‐questionnaires (1.24; 95% CI 1.17 to 1.32; P = 0.07, I2 = 41%), using a simple header (1.23; 95% CI 1.03 to 1.48), using textual representation of response categories (1.19; 95% CI 1.05 to 1.36), and giving a deadline (1.18; 95% CI 1.03 to 1.34). The odds of response tripled when a picture was included in an e‐mail (3.05; 95% CI 1.84 to 5.06; P = 0.27, I2 = 19%). The odds of response were reduced when "Survey" was mentioned in the e‐mail subject line (0.81; 95% CI 0.67 to 0.97; P = 0.33, I2 = 0%), and when the e‐mail included a male signature (0.55; 95% CI 0.38 to 0.80; P = 0.96, I2 = 0%).
Authors' conclusions
Health researchers using postal and electronic questionnaires can increase response using the strategies shown to be effective in this systematic review.
Plain language summary
Methods to increase response to postal and electronic questionnaires
Postal and electronic questionnaires are a relatively inexpensive way to collect information from people for research purposes. If people do not reply (so called 'non‐responders'), the research results will tend to be less accurate. This systematic review found several ways to increase response. People can be contacted before they are sent a postal questionnaire. Postal questionnaires can be sent by first class post or recorded delivery, and a stamped‐return envelope can be provided. Questionnaires, letters and e‐mails can be made more personal, and preferably kept short. Incentives can be offered, for example, a small amount of money with a postal questionnaire. One or more reminders can be sent with a copy of the questionnaire to people who do not reply.
Background
Postal questionnaires are widely used in the collection of data in epidemiological studies. When collecting information from large, geographically dispersed populations, the postal questionnaire is often the only financially viable option. Non‐response to postal questionnaires reduces the effective sample size and can introduce bias (Armstrong 1995). Because non‐response can affect the validity of epidemiological studies, assessment of response is an important dimension in the critical appraisal of health research. For the same reason, the identification of effective strategies to increase response to postal questionnaires could improve the quality of health research. We sought to identify such strategies by conducting a systematic review of randomised controlled trials.
Objectives
To quantify the effects of methods to increase response to postal and electronic questionnaires.
Methods
Criteria for considering studies for this review
Types of studies
All unconfounded randomised controlled trials of methods designed to increase response to postal or electronic questionnaires. A postal questionnaire was defined as a questionnaire that is delivered to a person's home or work address by a distribution system. This includes questionnaires delivered by any postal service including internal organisational mail and those hand delivered to a person's address. It does not include questionnaires distributed at, for example, a shop or in a doctor's office. The 2008 update to this review included randomised controlled trials of questionnaires distributed by electronic mail, and strategies designed to improve response to online or web surveys.
Types of data
Any population (e.g. patients or healthcare providers, and including any participants of non‐health studies).
Types of methods
Any methods designed to increase response to postal or electronic questionnaires. Strategies requiring telephone contact as a follow‐up technique are included but those requiring home visits are not.
Types of outcome measures
Proportion of completed, or partially completed questionnaires returned after the first mailing.
Proportion of completed, or partially completed questionnaires returned after all mailings.
Proportion of participants logging‐in, or clicking the hyperlink to visit the online survey.
Proportion of participants submitting the online survey.
Search methods for identification of studies
We identified trials by searching 14 electronic bibliographic databases, the reference lists of all identified trials, reference lists of relevant meta‐analyses, contacting the authors of included trials and by handsearching. Full details of the search strategies used are included inAppendix 1.
Data collection and analysis
Trial identification
Two authors of this review examined the titles, abstracts and key words of all records identified from electronic bibliographic databases.
Quality assessment
Since the quality of allocation concealment affects the results of studies, two authors of the review scored quality on the scale used by Schulz (Schulz 1995) as shown below, assigning C to poorest quality and A to best quality:
A ‐ trials deemed to have taken adequate measures to conceal allocation (i.e. central randomisation; computer‐generated address labels; or other description that contained elements that would ensure concealment). B ‐ trials in which the authors either did not report an allocation concealment approach at all or reported an approach that did not fall into one of the other categories. C ‐ trials in which concealment was inadequate (such as alternation or reference to case record numbers or to dates of birth). Where the method used to conceal allocation was not clearly reported, the author was contacted, if possible, for clarification. We then compared the scores allocated and resolved differences by discussion.
Data extraction
Two authors of this review independently extracted data from eligible reports using a standard proforma, with disagreements resolved by a third author of the review. We extracted data on the type of intervention evaluated, the number randomised to intervention or control groups, the quality of allocation concealment, and the types of participants, materials and follow‐up methods used. Two outcomes were used to estimate the effect of each intervention on response: the proportion of questionnaires returned after the first mailing and the proportion returned after all follow‐up contacts were complete. We wrote to the authors of reports where information was missing. We excluded trials in which we could not confirm that random allocation had been used to allocate participants.
Analysis
We classified and analysed interventions were classified and analysed under broad strategies to increase questionnaire response. In trials with factorial designs, we classified interventions under two or more strategies. When interventions were evaluated at more than two levels (e.g. highly, moderately and slightly personalised questionnaires), we combined the upper levels, creating a dichotomy. For example, we compared response to the least personalised questionnaire with the combined response for the moderately and highly personalised questionnaires. Monetary incentives were defined as any incentive that could be used by participants as money (i.e. cash or cheques). Incentives such as a donation to charity, or entrance into a lottery, were classified as 'non‐monetary' incentives.
We made additional data analysesusing STATA statistical software (StataCorp 1999). For each strategy, we estimated pooled odds ratios using a random‐effects model. We calculated 95% confidence intervals and two‐sided P values for each outcome. We assessed evidence for selection bias using Egger's weighted regression method and Begg's rank correlation test and funnel plot. We assessed heterogeneity among trial odds ratios using a Chi2 test at a 5% significance level and the degree of inconsistency between trial results was quantified using the I2 statistic, as proposed by Higgins and Thompson (2002). The I2 statistic measures the percentage of variation across studies that is due to heterogeneity.
Results
Description of studies
Postal
We identified 481 eligible trials that evaluated 110 different strategies for increasing response to postal questionnaires. There were 75 strategies for which the trials included over 1000 participants.
Electronic
We identified 32 eligible trials that evaluated 27 different strategies for increasing response to electronic questionnaires. There were 20 strategies for which the trials included over 1000 participants.
See the table 'Characteristics of included studies' for further details.
Risk of bias in included studies
The method of randomisation was not known in the majority of eligible trials. Where information was available, the quality of allocation concealment was classified as C (inadequate) in 76 trials and as A (adequate) in 83 trials. The remaining trials were classified as B (unclear).
Effect of methods
Incentives ‐ What are participants offered? (Strategies 1 ‐ 11)
Postal
Ninety‐four trials (160,004 participants) evaluated the effect of a monetary incentive on questionnaire response. The odds of response were almost doubled using monetary incentives (odds ratio (OR) 1.87; 95% confidence interval (CI) 1.73 to 2.03). There was, however, significant heterogeneity among the trial results (P < 0.00001) (Analysis 1.2). Thirty‐seven trials (84,043 participants) evaluated the effect of a larger rather than a smaller monetary incentive on questionnaire response. The odds of response were a quarter higher when a larger monetary incentive was used (OR 1.26; 95% CI 1.14to 1.39) (Analysis 2.2). Thirteen trials (26,484 participants) evaluated the effect of offering a monetary rather than a non‐monetary incentive on questionnaire response. The odds of response were increased by over a half when a monetary incentive rather than a non‐monetary incentive was used (OR 95% CI 1.62; 1.39 to 1.88). There was significant heterogeneity among the trial results (P < 0.00001) (Analysis 3.2).
1.2. Analysis.
Comparison 1 Monetary incentive vs. no incentive, Outcome 2 Final response.
2.2. Analysis.
Comparison 2 Larger vs. smaller monetary incentive, Outcome 2 Final response.
3.2. Analysis.
Comparison 3 Monetary vs. non‐monetary incentive, Outcome 2 Final response.
Ninety‐four trials (135,934 participants) evaluated the effect of a non‐monetary incentive (e.g. key ring, lottery participation, offer of study results, etc.) on questionnaire response. The odds of response were increased by over a tenth when a non‐monetary incentive was used (OR 1.15; 95% CI 1.08 to 1.22). There was significant heterogeneity among the results of non‐monetary incentive trials (P < 0.00001) (Analysis 4.2). Seven trials (10,730 participants) evaluated the effect of a larger rather than a smaller non‐monetary incentive on questionnaire response. There was no evidence for an effect on response of using a larger non‐monetary incentive (OR 1.09; 95% CI 0.97 to 1.22) (Analysis 5.2).
4.2. Analysis.
Comparison 4 Non‐monetary incentive vs. no incentive, Outcome 2 Final response.
5.2. Analysis.
Comparison 5 Larger non‐monetary incentive vs. smaller, Outcome 2 Final response.
Twenty‐four trials (27,569 participants) evaluated the timing of incentives on questionnaire response. The odds of response increased by more than a half when incentives were given with questionnaires rather than only given after participants had returned their questionnaires (OR 1.61; 95% CI 1.36 to 1.89). There was significant heterogeneity among the trial results (P < 0.00001) (Analysis 8.2). Three trials (7924 participants) evaluated the effect of offering an incentive with the first rather than a subsequent mailing. The odds of response were increased by over a tenth when the incentive was offered with the first mailing (OR 1.14; 95% CI 1.02 to 1.28) (Analysis 9.2). Twelve trials (15,256 participants) evaluated the effect of offering survey results as an incentive. There was no evidence for an effect on response of offering the study results (OR 0.90; 95% CI 0.76 to 1.07) (Analysis 11.2).
8.2. Analysis.
Comparison 8 Incentive with questionnaire vs. on response, Outcome 2 Final response.
9.2. Analysis.
Comparison 9 Incentive with first vs. subsequent mailing, Outcome 2 Final response.
11.2. Analysis.
Comparison 11 Offer of survey results vs. no offer, Outcome 2 Final response.
Electronic
One trial (1102 participants) evaluated the effect of a monetary incentive on electronic questionnaire response. There was no evidence for an effect on response of using monetary incentives (OR 1.19; 95% CI 0.82 to 1.75) (Analysis 1.4). Six trials (17,493 participants) evaluated the effect of a non‐monetary incentive (e.g. Amazon gift cards, lottery participation, personal digital assistant, early grade feedback, etc.) on e‐questionnaire response. The odds of response were almost doubled when a non‐monetary incentive was used (OR 1.72; 95% CI 1.09 to 2.72) (Analysis 4.4). Seven trials (31,454 participants) evaluated the effect of a larger rather than a smaller non‐monetary incentive on e‐questionnaire response. There was no evidence for an effect on response of using a larger non‐monetary incentive (OR 0.95; 95% CI 0.78 to 1.15) (Analysis 5.4). Two trials (2856 participants) evaluated the effect of a monetary rather than a non‐monetary incentive on e‐questionnaire response. There was no evidence for an effect on response of using a monetary rather than non‐monetary incentive (OR 0.77; 95% CI 0.48 to 1.23) (Analysis 3.4).
1.4. Analysis.
Comparison 1 Monetary incentive vs. no incentive, Outcome 4 e ‐ Submission.
4.4. Analysis.
Comparison 4 Non‐monetary incentive vs. no incentive, Outcome 4 e ‐ Submission.
5.4. Analysis.
Comparison 5 Larger non‐monetary incentive vs. smaller, Outcome 4 e ‐ Submission.
3.4. Analysis.
Comparison 3 Monetary vs. non‐monetary incentive, Outcome 4 e ‐ Submission.
One trial (2233 participants) evaluated the effect of immediate notification of lottery results compared to delayed notification on e‐questionnaire response. The odds of response were increased by almost a half when lottery results were immediately notified (OR 1.37; 95% CI 1.13 to 1.65) (Analysis 6.4). Two trials (4721 participants) evaluated the effect of higher denominations of currencies in a monetary lottery compared to lower denominations on e‐questionnaire response. There was no evidence for an effect on response of offering higher denominations in a monetary lottery (OR 1.00; 95% CI 0.87 to 1.14) (Analysis 7.4).
6.4. Analysis.
Comparison 6 Immediate notification of lottery results vs. delayed notification, Outcome 4 e ‐ Submission.
7.4. Analysis.
Comparison 7 Higher denominations in monetary lottery incentives vs. lower, Outcome 4 e ‐ Submission.
Three trials (1401 participants) evaluated the timing of incentives on e‐questionnaire response. There was no evidence for an effect on response when incentives were given with questionnaires rather than only given after participants had submitted their e‐questionnaires (OR 1.08; 95% CI 0.77 to 1.50) (Analysis 8.4). One trial (1061 participants) evaluated the combined effect of conditional and unconditional incentives compared to conditional incentives alone. There was no evidence for an effect on response of using the combined incentives (OR 1.19; 95% CI 0.92 to 1.54) (Analysis 10.4). A single trial (2332 participants) evaluated the effect of offering survey results as an incentive. The odds of response increased by almost a half when offer of results was used (OR 1.36; 95% CI 1.15 to 1.61) (Analysis 11.4).
8.4. Analysis.
Comparison 8 Incentive with questionnaire vs. on response, Outcome 4 e ‐ Submission.
10.4. Analysis.
Comparison 10 Unconditional and conditional incentives vs. conditional incentives, Outcome 4 e ‐ Submission.
11.4. Analysis.
Comparison 11 Offer of survey results vs. no offer, Outcome 4 e ‐ Submission.
Length ‐ How long is the questionnaire? (Strategies 12 & 13)
Postal
Fifty‐six trials (60,119 participants), including two unpublished trials, evaluated the effect of questionnaire length on response. The odds of response increased by more than a half using shorter questionnaires (OR 1.64; 95% CI 1.43 to 1.87). Heterogeneity among trial results was apparent on inspection of the forest plot and Chi2 test result (P < 0.00001) (Analysis 12.2). One trial (600 participants) evaluated the effect on questionnaire response of using a double postcard compared to one page. The odds ratio decreased by a half when a double postcard was used (OR 0.47; 95% CI 0.34 to 0.66) (Analysis 13.2).
12.2. Analysis.
Comparison 12 Shorter vs. longer questionnaire, Outcome 2 Final response.
13.2. Analysis.
Comparison 13 Double postcard vs. one page, Outcome 2 Final response.
Electronic
Two trials (7589 participants) evaluated the effect of the length of e‐questionnaire on response. The odds of response increased by over a half when using shorter e‐questionnaires (OR 1.73; 95% CI 1.40 to 2.13) (Analysis 12.4).
12.4. Analysis.
Comparison 12 Shorter vs. longer questionnaire, Outcome 4 e ‐ Submission.
Appearance ‐ How does the questionnaire look? (Strategies 14 ‐ 43)
Postal
Fifty‐eight trials (60,184 participants) evaluated the effect on questionnaire response of making questionnaire materials more personal, such as signing letters by hand. The odds of response were increased by more than a tenth with a more personalised approach to participants (OR 1.14; 95% CI 1.07 to 1.22). There was, however, significant heterogeneity among the results of these trials (P < 0.0001) (Analysis 14.2). Fourteen trials (15,006 participants) evaluated the effect of cover letters bearing a hand‐written signature compared to those that are typed or scanned or printed. The odds of response increased by a quarter using hand‐written signatures (OR 1.24; 95% CI 1.08 to 1.41) (Analysis 15.2). Seven trials (5091 participants) evaluated the effect of hand‐written address label compared to computer‐printed label. The odds of response increased by a quarter when using the hand‐written labelled questionnaire (OR 1.25; 95% CI 1.08 to 1.45) (Analysis 16.2). Two trials (1030 participants) evaluated the presence of a signature within the questionnaire. There was no evidence for an effect on response of using a signature within the questionnaire (OR 1.34; 95% CI 0.97 to 1.85) (Analysis 17.2). Eight trials (4134 participants) evaluated the effect of including an identifying feature, such as a participant's name or identity number, on questionnaire response. There was no evidence for an effect on response of using an identifying feature (OR 1.12; 95% CI 0.82 to 1.52) (Analysis 18.2).
14.2. Analysis.
Comparison 14 More vs. less personalised, Outcome 2 Final response.
15.2. Analysis.
Comparison 15 Hand‐written vs. typed/facsimile/scanned/printed signature on covering letter, Outcome 2 Final response.
16.2. Analysis.
Comparison 16 Hand‐written address vs. computer‐printed , Outcome 2 Final response.
17.2. Analysis.
Comparison 17 Signed vs. unsigned, Outcome 2 Final response.
18.2. Analysis.
Comparison 18 Identifying feature on return vs. none, Outcome 2 Final response.
Five trials (8637 participants) evaluated the effect on questionnaire response of using brown envelopes compared to white. There was no evidence for an effect on response of using brown envelope (OR 1.23; 95% CI 0.81 to 1.87) (Analysis 20.2). Fourteen trials (41,421 participants) evaluated the effect on response of using questionnaires printed on coloured paper. There was no evidence for an effect on response of using coloured questionnaire (OR 1.04; 95% CI 0.99 to 1.10) (Analysis 21.2). Three trials (7040 participants) evaluated the effect of using coloured ink, compared with black or blue ink, on questionnaire response. There was no evidence for an effect on response of using coloured ink (OR 1.16; 95% CI 0.95 to 1.42) (Analysis 22.2). Two trials (2356 participants) evaluated the effect of a coloured letterhead compared to a black and white letterhead. There was no evidence for an effect on response of using a coloured letterhead (OR 1.08; 95% CI 0.91 to 1.28) (Analysis 23.2). A single trial (320 participants) evaluated the effect of an illustration on the cover of the questionnaire largely in black, versus largely in white. The odds of response increased by more than a half when using an illustration on the cover of the questionnaire that was largely in black (OR 1.62; 95% CI 1.04 to 2.53) (Analysis 24.2).
20.2. Analysis.
Comparison 20 Brown vs. white envelope, Outcome 2 Final response.
21.2. Analysis.
Comparison 21 Coloured vs. white questionnaire, Outcome 2 Final response.
22.2. Analysis.
Comparison 22 Coloured vs. standard (black/blue) ink, Outcome 2 Final response.
23.2. Analysis.
Comparison 23 Coloured vs. black & white letterhead, Outcome 2 Final response.
24.2. Analysis.
Comparison 24 Illustration on cover of q'aire largely in black vs. largely in white, Outcome 2 Final response.
Three trials (5681 participants) evaluated the effect on response of using a booklet compared to stapled pages. There was no evidence for an effect on response of using a booklet (OR 1.10; 95% CI 0.99 to 1.23) (Analysis 25.2). Two trials (2145 participants) evaluated the effect of the paper size of the questionnaire on response. There was no evidence for an effect on response of using a large paper size (OR 0.88; 95% CI 0.56 to 1.39) (Analysis 26.2). A single trial (176 participants) evaluated the effect on questionnaire response of printing the questionnaire using dot matrix compared to a letter‐quality print. There was no evidence for an effect of response of using the dot matrix print (OR 1.15; 95% CI 0.63 to 2.10) (Analysis 27.2). Two trials (1039 participants) evaluated the effect of the questionnaire being printed on a high quality or thicker paper, compared to standard quality or thin paper. There was no evidence for an effect on response of using a high quality or a thicker paper (OR 0.80; 95% CI 0.60 to 1.06) (Analysis 28.2). Four trials (4966 participants) evaluated the effect of using a single‐sided questionnaire compared to a double‐sided questionnaire. The odds of response increased by almost a quarter when a single‐sided questionnaire was used (OR 1.22; 95% CI 1.01 to 1.47) (Analysis 29.2). One trial (650 participants) evaluated the effect on response of using a larger font compared to a smaller font. There was no evidence for an effect on response of using larger font (OR 1.26; 95% CI 0.87 to 1.82) (Analysis 30.2).
25.2. Analysis.
Comparison 25 Folder or booklet vs. stapled pages, Outcome 2 Final response.
26.2. Analysis.
Comparison 26 Large paper size vs. small, Outcome 2 Final response.
27.2. Analysis.
Comparison 27 Dot matrix print vs. letter quality print, Outcome 2 Final response.
28.2. Analysis.
Comparison 28 Questionnaire printed on high vs. standard quality paper or thick paper vs. thin, Outcome 2 Final response.
29.2. Analysis.
Comparison 29 Single vs. double‐sided questionnaire, Outcome 2 Final response.
30.2. Analysis.
Comparison 30 Large font size vs. small, Outcome 2 Final response.
A single trial (1000 participants) compared the presence of study logo on several items in the mailing package to its presence in the questionnaire only. There was no evidence for an effect on response of using study logo on several items in the mailing package (OR 0.92; 95% CI 0.72 to 1.18) (Analysis 31.2). Four trials (3710 participants) evaluated the effect of the presence of a picture in the questionnaire. There was no evidence for an effect on response of using a picture (OR 1.07; 95% CI 0.76 to 1.53) (Analysis 32.2). One trial (280 participants) evaluated the effect on response of including a cartoon in the questionnaire. There was no evidence for an effect on response of including a cartoon (OR 1.00; 95% CI 0.62 to 1.62) (Analysis 34.2). Two trials (316 participants) evaluated the effect of using a questionnaire in matrix form compared to standard form. There was no evidence for an effect on response using the matrix form (OR 0.58; 95% CI 0.29 to 1.16) (Analysis 35.2). One trial (259 participants) evaluated the effect on response of questions ordered by time period compared to those not ordered by time period. There was no evidence for an effect on response of using questionnaires where questions are ordered by time period (OR 1.48; 95% CI 0.84 to 2.59) (Analysis 36.3).
31.2. Analysis.
Comparison 31 Study logo on several items in the mailing package vs. on questionnaire only, Outcome 2 Final response.
32.2. Analysis.
Comparison 32 Picture of researcher/images vs. none, Outcome 2 Final response.
34.2. Analysis.
Comparison 34 Cartoons included vs. not, Outcome 2 Final response.
35.2. Analysis.
Comparison 35 Matrix vs. standard form, Outcome 2 Final response.
36.3. Analysis.
Comparison 36 Questions ordered by time period vs. other order, Outcome 3 Final response.
Electronic
Twelve trials (48,910 participants) evaluated the effect on e‐questionnaire response by addressing the salutations in the cover letters accompanying the questionnaires personally, or by giving a touch of personalisation to the cover letters. The odds of response were increased by about a quarter when personalised approach was adopted (OR 1.24; 95% CI 1.17 to 1.32) (Analysis 14.4). Two trials (720 participants) evaluated the effect of the presence of a picture in the e‐mail. The odds of response tripled when a picture was sent in the e‐mail (OR 3.05; 95% CI 1.84 to 5.06) (Analysis 32.4). The same trials (520 participants) evaluated the effect of response when a more attractive picture was used compared to a less attractive picture. There was no evidence for an effect on response of using a more attractive picture (OR 3.44; 95% CI 0.72 to 16.49) (Analysis 33.4).
14.4. Analysis.
Comparison 14 More vs. less personalised, Outcome 4 e ‐ Submission.
32.4. Analysis.
Comparison 32 Picture of researcher/images vs. none, Outcome 4 e ‐ Submission.
33.4. Analysis.
Comparison 33 Attractive vs. less attractive picture, Outcome 4 e ‐ Submission.
Two trials (6152 participants) evaluated the presence of a topic in the subject line of the e‐mail compared to a blank subject line. There was no evidence for an effect on response of using a topic in the subject line (OR 0.84; 95% CI 0.71 to 1.01) (Analysis 37.2). Two trials (3845 participants) evaluated the presence of "Survey" as the subject line compared to a blank subject line. The odds of response decreased by a fifth when "Survey" was mentioned in the subject line (OR 0.81; 95% CI 0.67 to 0.97) (Analysis 38.2). One trial (6090 participants) evaluated the effect of sending the e‐mails in text file formats compared to HTML. There was no evidence for an effect on response of using text file format (OR 1.00; 95% CI 0.84 to 1.19) (Analysis 39.2). The same trial (6090 participants) evaluated the presence of using a white background in the e‐mail compared to a black background. The odds of response increased by over a quarter when a white background was used (OR 1.31; 95% CI 1.10 to 1.56) (Analysis 40.2).
37.2. Analysis.
Comparison 37 Subject line vs. blank, Outcome 2 e ‐ Submission.
38.2. Analysis.
Comparison 38 "Survey" subject line vs. blank, Outcome 2 e ‐ Submission.
39.2. Analysis.
Comparison 39 Text vs. HTML file formats, Outcome 2 e ‐ Submission.
40.2. Analysis.
Comparison 40 White background vs. black, Outcome 2 e ‐ Submission.
One trial (6090 participants) evaluated the effect of a including a header compared to no header in the e‐mail. There was no evidence for an effect on response of using a header (OR 1.13; 95% CI 0.90 to 1.41) (Analysis 41.2). The same trial (5075 participants) evaluated the effect of a simple header compared to a complex header. The odds of response increased by almost a quarter when a simple header was used (OR 1.23; 95% CI 1.03 to 1.48) (Analysis 42.2). One trial (5413 participants) evaluated the effect of textual presentation of response categories compared to visual presentation of response categories. The odds of response increased by almost a fifth when textual presentation was used (OR 1.19; 95% CI 1.05 to 1.36) (Analysis 43.4).
41.2. Analysis.
Comparison 41 Header vs. no header, Outcome 2 e ‐ Submission.
42.2. Analysis.
Comparison 42 Simple vs. complex header, Outcome 2 e ‐ Submission.
43.4. Analysis.
Comparison 43 Textual presentation of response categories vs. visual presentation, Outcome 4 e ‐ Submission.
Delivery ‐ How are the questionnaires received or returned? (Strategies 44 ‐ 60)
Postal
Six trials (13,964 participants) evaluated the effect on questionnaire response of using stamps on out‐going envelopes compared to franked envelopes. There was no evidence for an effect on response of using stamps on outgoing envelopes (OR 0.95; 95% CI 0.88 to 1.03) (Analysis 44.2). Two trials (8300 participants) evaluated the effect on questionnaire response of using first class compared to other classes of postage. The odds of response were increased by over one‐tenth using first class postage (OR 1.11; 95% CI 1.02 to 1.21) (Analysis 45.2). Five trials (5461 participants) evaluated the effect on questionnaire response of using commemorative stamps rather than standard stamps on return envelopes. There was no evidence for an effect on response of using commemorative stamps (OR 0.92; 95% CI 0.81 to 1.06) (Analysis 46.2). Fifteen trials (18,931 participants) evaluated the effect on questionnaire response of using a special delivery service (including recorded, registered and certified delivery), rather than standard delivery. The odds of response increased by more than a half when special delivery was used (OR 1.76; 95% CI 1.43 to 2.18). Results were significantly heterogeneous (P < 0.00001) (Analysis 47.2).
44.2. Analysis.
Comparison 44 Stamped vs. franked outward envelope, Outcome 2 Final response.
45.2. Analysis.
Comparison 45 First vs. second/third class outward mailing, Outcome 2 Final response.
46.2. Analysis.
Comparison 46 Commemorative/race‐specific vs. ordinary stamp on return envelope, Outcome 2 Final response.
47.2. Analysis.
Comparison 47 Certified/special delivery vs. regular outward mailing, Outcome 2 Final response.
Twenty‐seven trials (48,612 participants) evaluated the effect on questionnaire response of using a stamped return envelope compared to a pre‐paid business or franked reply envelope. The odds of response increased by a quarter when stamps were used (OR 1.24; 95% CI 1.14 to 1.35). There was significant heterogeneity between the trial results (P < 0.001) (Analysis 48.2). One trial (205 participants) evaluated the effect of using priority stamps on return envelopes compared to using a first class stamp. The odds of response decreased by more than a half when priority stamps were used (OR 0.26; 95% CI 0.14to 0.46) (Analysis 49.2). One trial (800 participants) evaluated the effect of using a first class stamp on return envelopes compared to a second class stamp. There was no evidence for an effect on response of using first class stamp on return envelope (OR 0.91; 95% CI 0.69 to 1.21) (Analysis 50.2).
48.2. Analysis.
Comparison 48 Stamped vs. business reply/franked return envelope, Outcome 2 Final response.
49.2. Analysis.
Comparison 49 Priority stamps vs. first‐class stamps on return envelope, Outcome 2 Final response.
50.2. Analysis.
Comparison 50 First vs. second class stamp on return envelope, Outcome 2 Final response.
A single trial (510 participants) evaluated the use of multiple stamps on return envelopes compared to a single stamp. The odds of response increased by almost a half when multiple stamps were used (OR 1.44; 95% CI 1.01 to 2.04) (Analysis 51.2). Four trials (4094 participants) evaluated the effect on questionnaire response of providing any sort of pre‐paid return envelope rather than none. There was no evidence for an effect on response of including pre‐paid envelopes (OR 1.09; 95% CI 0.71 to 1.68). There was significant heterogeneity among the trial results (P < 0.0001) (Analysis 53.2). A single trial (147 participants) evaluated the effect of stamped addressed return envelopes compared to only including an address label. In this trial there was no evidence for an effect on response of using a stamped addressed return envelope (OR 0.86; 95% CI 0.45 to 1.65) (Analysis 54.2).
51.2. Analysis.
Comparison 51 Multiple stamps vs. single stamp on return envelope, Outcome 2 Final response.
53.2. Analysis.
Comparison 53 Pre‐paid return envelope vs. not pre‐paid, Outcome 2 Final response.
54.2. Analysis.
Comparison 54 Stamped addressed return envelope vs. address label only included, Outcome 2 Final response.
Two trials (1140 participants) evaluated the effect on response of sending questionnaires to the participant's work address rather than to their home address. There was no evidence for an effect on response of sending questionnaires to work addresses (OR 1.16; 95% CI 0.89 to 1.52) (Analysis 52.2). Two trials (11,781 participants) evaluated the effect of using a window envelope on questionnaire response. There was no evidence for an effect on response of using window envelopes (OR 0.96; 95% CI 0.61 to 1.49) (Analysis 56.2). A single trial (1200 participants) evaluated the effect on questionnaire response of sending the questionnaire in a larger envelope compared to a standard or smaller envelope. There was no evidence for an effect of response of using larger envelopes (OR 0.93; 95% CI 0.74 to 1.17) (Analysis 55.2). A single trial (4213 participants) evaluated the effect of providing optional Internet response along with the traditional postal response. There was no evidence for an effect on response of providing optional Internet response (OR 0.93; 95% CI 0.82 to 1.05) (Analysis 57.2).
52.2. Analysis.
Comparison 52 Questionnaire sent to work vs. home address, Outcome 2 Final response.
56.2. Analysis.
Comparison 56 Window vs. regular envelope, Outcome 2 Final response.
55.2. Analysis.
Comparison 55 Q'aire mailed in large vs. standard/small envelope, Outcome 2 Final response.
57.2. Analysis.
Comparison 57 Postal + optional Internet response vs. only postal response, Outcome 2 Final response.
One trial (504) evaluated the effect of questionnaires being mailed on Monday compared to being sent on Friday. There was no evidence for an effect on response of sending the questionnaire on Monday (OR 0.83; 95% CI 0.58 to 1.17) (Analysis 58.2). One trial (460 participants) evaluated the effect of a questionnaire being received on a Monday, compared to being received on a Friday. There was no evidence for an effect on response of questionnaires being received on a Monday (OR 1.00; 95% CI 0.64 to 1.56) (Analysis 59.2). Two trials (2324 participants) evaluated the effect on response of questionnaires being sent one to five weeks after discharge from hospital, compared to being sent after 9 to 14 weeks. There was no evidence for an effect on response of questionnaires being sent sooner after discharge from hospital (OR 2.26; 95% CI 0.69 to 7.37) (Analysis 60.2).
58.2. Analysis.
Comparison 58 Questionnaire mailed on Monday vs. Friday, Outcome 2 Final response.
59.2. Analysis.
Comparison 59 Questionnaire received on Monday vs. Friday, Outcome 2 Final response.
60.2. Analysis.
Comparison 60 Q'aire sent 1‐5 weeks vs. 9‐14 weeks after hospital discharge, Outcome 2 Final response.
Contact ‐ Methods and number of requests for participation (Strategies 61 ‐ 68)
Postal
Forty‐seven trials (79,651 participants) evaluated the effect on response of contacting participants before sending questionnaires. The odds of response were increased by a half when participants were pre‐notified (OR 1.45; 95% CI 1.29 to 1.63). There was significant heterogeneity among the trial results (P < 0.00001) (Analysis 61.2). Seven trials (3322 participants) evaluated the effect on response of pre‐notification by telephone compared to by post. There was no evidence for an effect on response when participants were pre‐contacted by telephone instead of by post (OR 1.18; 95% CI 0.77 to 1.80) (Analysis 62.2).
61.2. Analysis.
Comparison 61 Pre‐contact vs. no pre‐contact, Outcome 2 Final response.
62.2. Analysis.
Comparison 62 Pre‐contact by phone vs. mail, Outcome 2 Final response.
Nineteen trials (32,778 participants) evaluated the effect on questionnaire response of follow‐up contact (e.g. repeat mailings or telephone calls) with participants who do not respond to the initial questionnaire. The odds of response increased by more than a quarter when follow‐up contact was used (OR 1.35; 95% CI 1.18 to 1.55). There was significant heterogeneity among the results and both Begg's and Egger's tests indicated evidence of selection bias (Analysis 63.2). Eleven trials (8619 participants) evaluated the effect on response of providing participants with another copy of the questionnaire during postal follow up. The odds of response were increased by a half when questionnaires were included during postal follow up (OR 1.46; 95% CI 1.13 to 1.90). There was significant heterogeneity among these results (P < 0.00001) (Analysis 64.2).
63.2. Analysis.
Comparison 63 Follow up vs. no follow up, Outcome 2 Final response.
64.2. Analysis.
Comparison 64 Postal follow‐up including vs. excluding q'aire, Outcome 2 Final response.
Five trials (2254 participants) evaluated the effect on questionnaire response of using telephone rather than postal follow up. There was no evidence for an effect on response of using telephone follow up (OR 0.86; 95% CI 0.54 to1.36) (Analysis 65.2). Three trials (13,922 participants) evaluated the effect on response of a telephone reminder compared to no reminder. There was no evidence for an effect on response of using a telephone reminder (OR 1.29; 95% CI 0.85 to 1.96) (Analysis 66.2). Three trials (9947 participants) evaluated the effect of an SMS reminder compared to a postcard reminder. The odds of response increased by half when an SMS reminder was used (OR 1.49; 95% CI 1.23 to 1.81) (Analysis 67.2).
65.2. Analysis.
Comparison 65 Follow up by phone vs. mail, Outcome 2 Final Response.
66.2. Analysis.
Comparison 66 Telephone reminder vs. no reminder, Outcome 2 Final response.
67.2. Analysis.
Comparison 67 SMS vs. postcard reminder, Outcome 2 Final response.
Two trials (1608 participants) evaluated the effect on questionnaire response of using a follow‐up interval of less than 31 days compared to a follow‐up interval of 31 to 60 days. There was no evidence for an effect on response when a follow‐up interval of less than 31 days was used (OR 0.97; 95% CI 0.75 to 1.26) (Analysis 68.2).
68.2. Analysis.
Comparison 68 Follow‐up interval < 31 days vs. 31‐60 days, Outcome 2 Final response.
Content ‐ Nature and style of questions (Strategies 69 ‐ 93)
Postal
Ten trials (21,393 participants) evaluated the effect on response of including a 'sensitive' question in a questionnaire. The odds of response were reduced by nearly one‐tenth when sensitive questions were included (OR 0.94; 95% CI 0.88 to 1.00) (Analysis 69.2). A single trial (5817 participants) evaluated the effect on response of placing the more relevant questions at the start of the questionnaire. The odds of response were increased by a quarter when more relevant questions were placed first (OR 1.23; 95% CI 1.10 to 1.37) (Analysis 70.2). Three trials (11,435 participants) evaluated the effect on response of placing the most general questions at the start of the questionnaire. There was no evidence for an effect on response of placing general questions first (OR 0.95; 95% CI 0.83 to 1.09) (Analysis 71.2).
69.2. Analysis.
Comparison 69 Sensitive questions vs. no/fewer/less sensitive questions asked, Outcome 2 Final response.
70.2. Analysis.
Comparison 70 More relevant questions first vs. last, Outcome 2 Final response.
71.2. Analysis.
Comparison 71 Most general question first vs. last, Outcome 2 Final response.
Four trials (3598 participants) evaluated the effect on questionnaire response of placing questions asking for demographic information first. There was no evidence for an effect on response of placing demographic items first (OR 1.08; 95% CI 0.94 to 1.25) (Analysis 72.2). Two trials (3182 participants) evaluated the effect on response of placing the easiest questions at the start of the questionnaire. The odds of response were increased by over a half when the easiest questions were presented first (OR 1.61; 95% CI 1.14 to 2.26) (Analysis 73.2).
72.2. Analysis.
Comparison 72 Demographic items first vs. last, Outcome 2 Final response.
73.2. Analysis.
Comparison 73 Easier questions first vs. last, Outcome 2 Final response.
A single trial (3540 participants) evaluated the effect on response of using a more 'user‐friendly' questionnaire. The odds of response were increased by almost a half using user‐friendly questionnaires (OR 1.46; 95% CI 1.21 to 1.75) (Analysis 74.2).Three trials (2711 participants) evaluated the effect on response of using a more 'interesting' or high salient questionnaire (e.g. asking questions particularly relevant to the study participants). The odds of response were doubled using more interesting questionnaires (OR 2.00; 95% CI 1.32 to 3.04) (Analysis 75.2).
74.2. Analysis.
Comparison 74 User friendly vs. standard questionnaire, Outcome 2 Final response.
75.2. Analysis.
Comparison 75 More interesting vs. less or high salient topic vs. low, Outcome 2 Final response.
Three trials (1764 participants) evaluated the effect on questionnaire response of using open‐ended rather than closed questions. The odds of response were reduced by more than half when open‐ended questions were used (OR 0.31; 95% CI 0.09 to 1.04) (Analysis 76.2). One trial (300 participants) evaluated the effect of using open‐ended items first compared to other items first. There was no evidence for an effect on response of using open‐ended items first (OR 1.26; 95% CI 0.73 to 2.19) (Analysis 77.2). One trial (300 participants) evaluated the effect of using closed‐ended items first compared to other items first. There was no evidence for an effect on response of using closed‐ended items first (OR 0.93; 95% CI 0.54 to 1.59) (Analysis 78.2).
76.2. Analysis.
Comparison 76 Open‐ended vs. closed questions, Outcome 2 Final response.
77.2. Analysis.
Comparison 77 Open‐ended items first vs. other items first, Outcome 2 Final response.
78.2. Analysis.
Comparison 78 Closed‐ended items first vs. other items first, Outcome 2 Final response.
A single trial (1360 participants) evaluated the effect on response of including 'don't know' boxes for questions. There was no evidence for an effect on response of including 'don't know' boxes (OR 1.03; 95% CI 0.82 to 1.29) (Analysis 79.2). Two trials (1125 participants) evaluated the effect on response of using a circle answer rather than tick box format on question responses. There was no evidence for an effect on response of using a circle answer format (OR 0.96; 95% CI 0.74 to 1.26) (Analysis 80.2). A single trial (6783 participants) evaluated the effect of listing response options in increasing order on questionnaire response. There was no evidence for an effect on response of listing response options in increasing order (OR 1.06; 95% CI 0.94 to 1.18) (Analysis 81.2).
79.2. Analysis.
Comparison 79 'Don't know' boxes included vs. not, Outcome 2 Final response.
80.2. Analysis.
Comparison 80 Circle answer vs. tick box format, Outcome 2 Final response.
81.2. Analysis.
Comparison 81 Response options listed in increasing vs. decreasing order, Outcome 2 Final response.
Two trials (3882 participants) evaluated the effect on response of using high frequency response alternatives compared to medium frequency response alternatives. There was no evidence for an effect on response when high frequency response alternatives were used (OR 1.40; 95% CI 0.58 to 3.38) (Analysis 82.2). Another trial (654 participants) evaluated the effect on questionnaire response of using a 5‐step response scale compared to a 10‐step response scale. There was no evidence for an effect on response of using a 5‐step response scale (OR 0.78; 95% CI 0.52to 1.19) (Analysis 83.2).
82.2. Analysis.
Comparison 82 High vs. medium frequency response alternatives, Outcome 2 Final response.
83.2. Analysis.
Comparison 83 5‐step vs. 10‐step response scale, Outcome 2 Final response.
A single trial (1500 participants) evaluated the effect of using an individual‐item rather than a stem‐and‐leaf format on questionnaire response. There was no evidence for an effect on response of using individual item format (OR 0.88; 95% CI 0.70 to 1.10) (Analysis 85.2). One trial (400 participants), evaluated the horizontal orientation of response options compared to vertical orientation of response options. The odds of response tripled when horizontal orientation was used (OR 3.12; 95% CI 1.63 to 5.96) (Analysis 86.2). Four trials (7345 participants) evaluated the effect on response of using conventional mode of response technique compared to randomised response technique. There was no evidence for an effect on response of using the conventional mode of response technique (OR 1.52; 95% CI 0.85 to 2.72) (Analysis 87.2).
85.2. Analysis.
Comparison 85 Individual item vs. stem & leaf format, Outcome 2 Final response.
86.2. Analysis.
Comparison 86 Horizontal vs. vertical orientation of response options, Outcome 2 Final response.
87.2. Analysis.
Comparison 87 Conventional vs. randomised response technique, Outcome 2 Final response.
A single trial (1280 participants) evaluated the effect on response of asking 'factual' questions only compared to factual and attitudinal questions. The odds of response were increased by more than a quarter using factual questions only (OR 1.34; 95% CI 1.01 to 1.77) (Analysis 88.2). One trial (190 participants) evaluated the effect of including a teaser on the envelope. The odds of response increased by over three times when a teaser was used (OR 3.08; 95% CI 1.27 to 7.44) (Analysis 89.2).
88.2. Analysis.
Comparison 88 Factual questions only vs. factual and attitudinal questions, Outcome 2 Final response.
89.2. Analysis.
Comparison 89 Teaser on envelope vs. none, Outcome 2 Final response.
A single trial (1795 participants) evaluated the effect of sending the questionnaire with a supplement compared to sending the questionnaire alone. There was no evidence for an effect on response of sending questionnaire with a supplement (OR 0.86; 95% CI 0.70 to 1.07) (Analysis 90.2). Two trials (4943 participants) evaluated the effect on response of including a questionnaire for relatives. The odds of response were reduced by one third when a questionnaire for relatives was included (OR 0.67; 95% CI 0.60 to 0.76) (Analysis 91.2). One trial (414 participants) evaluated the effect of including a consent form with the questionnaire. There was no evidence for an effect on response of including a consent form (OR 1.32; 95% CI 0.89 to 1.95) (Analysis 92.2). Another trial (200 participants) evaluated the effect on response of using a multi‐option consent form compared to a standard consent form. There was no evidence for an effect on response of using a multi‐option consent form (OR 0.91; 95% CI 0.49 to 1.68) (Analysis 93.2).
90.2. Analysis.
Comparison 90 Questionnaire sent with supplement vs. alone, Outcome 2 Final response.
91.2. Analysis.
Comparison 91 Extra questionnaire for relatives included vs. not, Outcome 2 Final response.
92.2. Analysis.
Comparison 92 Consent form included vs. not, Outcome 2 Final response.
93.2. Analysis.
Comparison 93 Multi‐option vs. standard consent form, Outcome 2 Final response.
Electronic
One trial (2176 participants) evaluated the effect on response of using a more 'interesting' e‐questionnaire (e.g. asking questions particularly relevant to the study participants). The odds of response were almost doubled using a more interesting e‐questionnaire (OR 1.85; 95% CI 1.52 to 2.26) (Analysis 75.4).
75.4. Analysis.
Comparison 75 More interesting vs. less or high salient topic vs. low, Outcome 4 e ‐ Submission.
Origin ‐ Who sent the questionnaire? (Strategies 94 ‐ 100)
Postal
Fourteen trials (21,628 participants) evaluated the effect on response of university sponsorship. The odds of response were increased by more than a quarter when questionnaires originated from a university rather than an alternative source, such as a government department or commercial organisation (OR 1.32; 95% CI 1.13 to 1.54). There was significant heterogeneity between trial results (P < 0.00001) (Analysis 94.2). Ten trials (5644 participants) evaluated the effect on response when questionnaires were sent or signed by a more senior or well‐known person. There was no evidence for an effect on response when a more senior or well‐known person sent or signed the questionnaire (OR 1.05; 95% CI 0.89 to 1.23) (Analysis 95.2).
94.2. Analysis.
Comparison 94 University sponsor/source vs. other, Outcome 2 Final response.
95.2. Analysis.
Comparison 95 Sent or signed by more vs. less senior/well‐known person, Outcome 2 Final response.
A single trial (500 participants) evaluated the effect on questionnaire response of sending the questionnaire in a university printed envelope. There was no evidence for an effect on response of sending the questionnaire in a university printed envelope (OR 0.88; 95% CI 0.61 to 1.28) (Analysis 96.2). Two trials (924 participants) evaluated the effect on response of pre‐contact by a medical researcher compared to a non medical researcher. There was no evidence for an effect on response of pre‐contact by a medical researcher (OR 1.01; 95% CI 0.55 to 1.86) (Analysis 97.2). Two trials (1106 participants) evaluated the effect on response when questionnaires were sent from a GP rather than a research group. There was no evidence for an effect on response of sending questionnaires by a GP (OR 1.52; 95% CI 0.73 to 3.15) (Analysis 98.2).
96.2. Analysis.
Comparison 96 University printed envelope vs. plain, Outcome 2 Final response.
97.2. Analysis.
Comparison 97 Pre‐contact by medical researcher vs. non medical researcher, Outcome 2 Final response.
98.2. Analysis.
Comparison 98 Q'aire sent by GP vs. by research group, Outcome 2 Final response.
Five trials (5959 participants) evaluated the effect on response of whether the ethnicity of the name of the person sending the questionnaire was identifiable. There was no evidence for an effect on response when names were ethnically identifiable (OR 1.07; 95% CI 0.90 to 1.27) (Analysis 99.2). Two trials (3146 participants) evaluated the effect of sending the questionnaire by a male investigator compared to a female investigator. There was no evidence for an effect on response of sending the questionnaire by a male investigator (OR 1.07; 95% CI 0.72 to 1.58) (Analysis 100.2).
99.2. Analysis.
Comparison 99 Ethnically unidentifiable/white vs. other name, Outcome 2 Final response.
100.2. Analysis.
Comparison 100 Male vs. female investigator or male vs. female signature, Outcome 2 Final response.
Electronic
Two trials (3845 participants) evaluated the effect on e‐questionnaire response of university sponsorship. There was no evidence for an effect on e‐questionnaire response of using the university sponsorship (OR 0.84; 95% CI 0.69 to 1.01) (Analysis 94.4). Two trials (720 participants) evaluated the effect of sending the e‐questionnaire signed by a male compared to that signed by a female. The odds of response decreased by over a half when the e‐questionnaire was signed by a male (OR 0.55; 95% CI 0.38 to 0.80) (Analysis 100.4). Three trials (23,027 participants) evaluated the effect on response when e‐questionnaires were sent or signed by a more senior or well‐known person. There was no evidence for an effect on response when a more senior or well‐known person sent or signed the e‐questionnaire (OR 1.05; 95% CI 0.95 to 1.15) (Analysis 95.4).
94.4. Analysis.
Comparison 94 University sponsor/source vs. other, Outcome 4 e ‐ Submission.
100.4. Analysis.
Comparison 100 Male vs. female investigator or male vs. female signature, Outcome 4 e ‐ Submission.
95.4. Analysis.
Comparison 95 Sent or signed by more vs. less senior/well‐known person, Outcome 4 e ‐ Submission.
Communication ‐ What are participants told? (Strategies 101 ‐ 121)
Postal
One trial (25,000 participants) evaluated the effect on questionnaire response of providing participants with an assurance of confidentiality. The odds of response were increased by more than a quarter with an assurance of confidentiality (OR 1.33; 95% CI 1.24 to 1.42) (Analysis 101.2). One trial (468 participants) evaluated the effect on questionnaire response of including a statement that others had responded. There was no evidence for an effect on response when the statement was included (OR 1.12; 95% CI 0.76 to 1.65) (Analysis 102.2). Four trials (3555 participants) evaluated the effect on questionnaire response of offering participants the choice to opt‐out from the study. There was no evidence for an effect on response when participants could opt‐out (OR 0.92; 95% CI 0.66 to 1.28) (Analysis 103.2).
101.2. Analysis.
Comparison 101 Assurance of confidentiality vs. none, Outcome 2 Final response.
102.2. Analysis.
Comparison 102 Included statement that others had responded vs. no statement, Outcome 2 Final response.
103.2. Analysis.
Comparison 103 Choice to opt‐out from study vs. none, Outcome 2 Final response.
A single trial (2000 participants) evaluated the effect on response of providing instructions for completion of the questionnaire. There was no evidence for an effect on response when instructions were given (OR 0.89; 95% CI 0.74 to 1.06) (Analysis 104.2). Six trials (5661 participants) evaluated the effect on response of giving participants a deadline by which to respond. There was no evidence for an effect on response of giving deadlines (OR 1.00; 95% CI 0.84 to 1.19) (Analysis 105.2). Three trials (600 participants) evaluated the effect on response of mention of an obligation to respond compared to no mention of an obligation to respond. The odds of response increased by more than half with the mention of an obligation to respond (OR 1.61; 95% CI 1.16 to 2.22) (Analysis 106.2).
104.2. Analysis.
Comparison 104 Instructions given vs. not, Outcome 2 Final response.
105.2. Analysis.
Comparison 105 Response deadline given vs. no deadline, Outcome 2 Final response.
106.2. Analysis.
Comparison 106 Mention of obligation to respond vs. none, Outcome 2 Final response.
One trial (702 participants) evaluated the effect on response of questionnaires including a request for a telephone number. There was no evidence for an effect on response of requesting a telephone number (OR 1.00; 95% CI 0.65 to 1.54) (Analysis 107.2). One trial (200 participants) evaluated the effect of asking participants to respond on questionnaire itself compared to asking them to respond on a separate form. There was no evidence for an effect on response of asking the participants to respond on the questionnaire (OR 1.13; 95% CI 0.57 to 2.27) (Analysis 108.2).
107.2. Analysis.
Comparison 107 Request for telephone number vs. none, Outcome 2 Final response.
108.2. Analysis.
Comparison 108 Respond on questionnaire vs. on separate form, Outcome 2 Final response.
Seven trials (7053 participants) evaluated the effect on questionnaire response of telling participants that they would be contacted again if they did not respond. There was no evidence for an effect on response of questionnaire if mention of follow up was used (OR 1.02; 95% CI 0.91 to 1.15) (Analysis 109.2). Two trials (1907 participants) evaluated the effect on questionnaire response of requesting an explanation for non‐participation. There was no evidence for an effect on response of requesting an explanation for non‐participation (OR 1.14; 95% CI 0.83 to 1.57) (Analysis 110.2).
109.2. Analysis.
Comparison 109 Mention of follow‐up contact vs. none, Outcome 2 Final response.
110.2. Analysis.
Comparison 110 Explanation for non‐participation requested vs. not, Outcome 2 Final response.
One trial (600 participants) evaluated the effect on response of providing a time estimate for completion of the questionnaire. There was no evidence for an effect on response when a time estimation was provided (OR 1.10; 95% CI 0.76 to 1.58) (Analysis 111.2). Another trial (500 participants) evaluated the effect on response of a detailed cover letter compared to a brief cover letter. There was no evidence for an effect on response in using the detailed cover letter (OR 1.08; 95% CI 0.74 to 1.58) (Analysis 112.2). Two trials (1251 participants) evaluated the effect on response of the presence of an appeal or a pleading factor in the cover letter. There was no evidence for an effect on response of using an appeal (OR 1.06; 95% CI 0.79 to 1.42) (Analysis 113.2). A small trial (100 participants) evaluated the effect of a note requesting participants not to remove an ID Code. The odds of response decreased by more than a half when the note was added (OR 0.37; 95% CI 0.14 to 0.96) (Analysis 114.2).
111.2. Analysis.
Comparison 111 Time estimate for completion given vs. not, Outcome 2 Final response.
112.2. Analysis.
Comparison 112 Detailed vs. brief cover letter, Outcome 2 Final response.
113.2. Analysis.
Comparison 113 Appeal vs. none, Outcome 2 Final response.
114.2. Analysis.
Comparison 114 Note requesting not to remove ID code vs. none, Outcome 2 Final response.
A single trial (201 participants) evaluated the effect on response of a request for the participant's signature. There was no evidence for an effect on response when requesting participants' signatures (OR 1.19; 95% CI 0.65 to 2.18) (Analysis 115.2). One trial (395 participants) evaluated the effect of endorsing the questionnaire by eminent professionals in the field. The odds of response decreased by more than a quarter when an endorsement was used (OR 0.63; 95% CI 0.43 to 0.94) (Analysis 116.2). One trial (671 participants) evaluated the effect of a veiled threat in follow‐up letters. The odds of response doubled when a veiled threat was used (OR 2.09; 95% CI 1.49 to 2.93) (Analysis 117.2).
115.2. Analysis.
Comparison 115 Request for participant signature vs. none, Outcome 2 Final response.
116.2. Analysis.
Comparison 116 Questionnaire endorsed vs. not endorsed, Outcome 2 Final response.
117.2. Analysis.
Comparison 117 Veiled threat in follow‐up letter vs. none, Outcome 2 Final response.
Eight trials (10,908 participants) evaluated the effect on questionnaire response of stressing how response would benefit the sponsor. There was no evidence for an effect on response when stressing the benefits to the sponsor (OR 0.99; 95% CI 0.86 to 1.13). There was significant heterogeneity between trial results and both Begg's and Egger's tests indicated evidence of selection bias (Analysis 118.2). Nine trials (13,175 participants) evaluated the effect on questionnaire response of stressing how response would benefit the participant. There was no evidence for an effect on response when stressing the benefits to participants (OR 0.98; 95% CI 0.82 to 1.16) (Analysis 119.2). Ten trials (12,731 participants) evaluated the effect on questionnaire response of stressing how response would benefit society. There was no evidence for an effect on response of stressing the benefits to society (OR 1.09; 95% CI 0.92 to 1.29). Again, there was significant heterogeneity between trial results and both Begg's and Egger's tests indicated evidence of selection bias (Analysis 120.2). Two trials (2070 participants) evaluated the effect on response of questionnaires remaining anonymous compared with being identifiable. There was no evidence for an effect on response of questionnaires remaining anonymous (OR 0.96; 95% CI 0.66 to 1.39) (Analysis 121.2).
118.2. Analysis.
Comparison 118 Appeal stresses benefit to sponsor vs. other, Outcome 2 Final response.
119.2. Analysis.
Comparison 119 Appeal stresses benefit to respondent vs. other, Outcome 2 Final response.
120.2. Analysis.
Comparison 120 Appeal stresses benefit to society vs. other, Outcome 2 Final response.
121.2. Analysis.
Comparison 121 Anonymous vs. not anonymous, Outcome 2 Final response.
Electronic
One trial (8586 participants) evaluated the effect on e‐questionnaire response of including a statement that others had responded. The odds of response increased by half when the statement was included (OR 1.52; 95% CI 1.36 to 1.70) (Analysis 102.4). A single trial (8586 participants) evaluated the effect on e‐questionnaire response of giving participants a deadline by which to respond. The odds or response increased by over a tenth when giving a deadline (OR 1.18; 95% CI 1.03 to 1.34) (Analysis 105.4). Two trials (3844 participants) evaluated the effect of including an appeal, such as "request for help" in the subject line of the e‐maiI. There was no evidence for an effect on response of including an appeal in the subject line (OR 0.84; 95% CI 0.70 to 1.01) (Analysis 113.4).
102.4. Analysis.
Comparison 102 Included statement that others had responded vs. no statement, Outcome 4 e ‐ Submission.
105.4. Analysis.
Comparison 105 Response deadline given vs. no deadline, Outcome 4 e ‐ Submission.
113.4. Analysis.
Comparison 113 Appeal vs. none, Outcome 4 e ‐ Submission.
Discussion
Many reviews and meta‐analyses of strategies to increase response to postal questionnaires have appeared in the survey research literature over the last forty years. However, none was based on a systematic search of the published and unpublished literature and in particular they did not include the medical literature. The most comprehensive of these included 115 trials (Yammarino 1991), less than half the number of trials included in our review.
We have identified a range of strategies that increase response to postal and electronic questionnaires. The pooled intervention effects for some strategies are precise due to the large numbers of participants randomised in the combined trials. Before interpreting and applying the results of this review several methodological issues must be considered.
The identification and inclusion of all relevant trials in systematic reviews reduces random error in meta‐analyses and, because ease of identification of trials is associated with treatment effects, complete ascertainment may also reduce bias (Clarke 1994). We excluded some trials because we could not confirm that participants had been randomly allocated to intervention and control groups and have not examined whether the results of these trials differ systematically from the included trials. Although tests for selection bias were significant in five strategies, these results may be due to true heterogeneity between trial results, rather than bias in the selection of trials (Egger 1997).
Inadequate allocation concealment can bias the results of clinical trials (Schulz 1995). In our review, information on allocation concealment was unavailable for most of the included trials. If they were inadequately concealed, this may have biased the results.
It may be inappropriate to combine heterogeneous trial results to produce a single estimate of effect (Engels 2000). We found substantial heterogeneity among trial results in half of the strategies, and for these, the pooled odds ratios may not be meaningful. Variation between trial interventions and populations is likely to explain some of the heterogeneity. For example, among trials evaluating non‐monetary incentives, the types of incentive used are considerably heterogeneous including things such as donations to charity, lottery participation and free key rings or pens. Among trials evaluating monetary incentives, the amounts of money offered to participants vary between trials. A meta‐regression analysis has shown that monetary incentives can increase response to postal questionnaires but that the relation between the amount of money and response is not linear (Edwards 2005).
Among the trials evaluating shorter and longer questionnaires, the lengths of the questionnaires used varies between trials, some comparing one page with a two page alternative, and others comparing four or more pages with longer alternatives. In a meta‐regression analysis, most of the heterogeneity was explained by variation in the length of the questionnaires used in each trial (Edwards 2004). A subgroup analysis of the trials of personalisation in postal questionnaires found that response was increased by addressing participants by name on cover letters, and that the effect appears to be enhanced by including hand‐written signatures (Scott 2006).
Further analyses may reveal important sources of variation, for example, due to methodological quality, questionnaire topic, study age, or type of population. In this review, our aim was to systematically identify and critically appraise eligible trials, and to present the relevant data. We did not intend to produce single effect estimates for every strategy. For many strategies, although there is statistical heterogeneity, the directions of the effects were similar. For these strategies we cannot be sure about the size of the effect, but we can be reasonably confident that there was an effect on response.
We have chosen to use odds ratios in our analyses for methodological reasons. However, the practical implication of the odds ratio for a strategy is difficult to interpret without knowing the baseline response rate (without the strategy). Moreover, the odds ratio for a strategy might vary in relationship to the baseline response rate. Therefore, those conducting postal and electronic surveys should scrutinise the data in the relevant results tables closely if the magnitude of the effect that they might expect from using a specific strategy is an important consideration for them in deciding whether or not to use the strategy. A table showing the conversion of odds ratios to response proportions for a range of different baselines is included in Appendix 2.
Authors' conclusions
Implication for methodological research.
The results of this review show that questionnaire length has a substantial impact on non‐response, particularly when questionnaires are very short. In the context of outcome data collection in a clinical trial, the use of a short questionnaire would be expected to minimise non‐response, thus increasing the effective sample size and reducing sampling error. However, if the use of short questionnaires reduces the accuracy of the measurement process, the reduction in random error achieved by increased follow up would have to be traded‐off against increased random error due to using less precise measurement. Further research is required to quantify this trade‐off, so that outcome measures can be designed for use in clinical trials that minimise total random error (sampling error and measurement error).
This review examined the effectiveness of 121 different strategies to increase the response to postal and electronic questionnaires. The outcome of interest in this review was the overall response proportion and we did not examine the impact of factors that may influence the completeness of the returned questionnaires. However, factors that influence the readability of questionnaires, such as the number of syllables per word, words per sentence, typeface and font size may have an important effect on both the proportion of questions that are answered and indeed the overall response proportion.
Finally, although postal questionnaires are commonly used in the collection of data in epidemiological studies, the identification of strategies to increase response to other forms of survey data collection methods, such as personal or telephone interviews and electronic mail, is also important. In the recent update to this review we have included electronic questionnaires, and a review of the evidence for increasing response to telephone interviews is in preparation.
What's new
| Date | Event | Description |
|---|---|---|
| 12 May 2009 | New citation required but conclusions have not changed | The current update includes randomised controlled trials of questionnaires distributed by electronic mail, and strategies designed to improve response to online or web surveys. |
| 10 December 2008 | New search has been performed | This review has been updated (new search December 2007). The current update includes 481 eligible trials that evaluated 110 different strategies for increasing response to postal questionnaires and 32 eligible trials that evaluated 27 different strategies for increasing response to electronic questionnaires. A new search was re‐run February 2009 in MEDLINE and Psychinfo and 23 possibly eligible trials are listed under Studies awaiting classification. |
History
Protocol first published: Issue 2, 1999 Review first published: Issue 3, 2001
| Date | Event | Description |
|---|---|---|
| 27 December 2007 | Amended | Converted to new review format. |
| 20 February 2007 | New citation required and conclusions have changed | Substantive amendment |
Acknowledgements
This systematic review was supported by a grant from The BUPA Foundation and by a Nuffield Trust Short Term Fellowship, and was conducted with support from the editorial base of the Cochrane Injuries Group. The initial motivation for the review came from the need to find ways to ensure high rates of follow up in the MRC CRASH Trial. The authors would like to thank Dr Iain Chalmers, Professor Peter Sandercock, Professor Catherine Peckham and the MRC CRASH Trial Management Group for their help and advice with the study. The 2008 update to this review was supported by a second grant from The BUPA Foundation.
Appendices
Appendix 1. Search strategy
Electronic bibliographic databases
Search strategies were developed for use in a range of electronic bibliographic databases.
Database time period or version
Cochrane Controlled Trials Register 1999.3 CINAHL 1982 ‐ 1999.07 ERIC 1982 ‐ 1998.09 PsycLit 1887 ‐ 1999.09 Dissertation Abstracts 1861 ‐ 1999.08 MEDLINE 1966 ‐ 1999 EMBASE 1980 ‐ 1999.08
A. questionnair* or survey* or data collection B. respon* or return* C. remind* or letter* or postcard* or incentiv* or reward* or money* or monetary or payment* or lottery or raffle or prize or personalis* or sponsor* or anonym* or length or style* or format or appearance or color or colour or stationery or envelope or stamp* or postage or certified or registered or telephon* or telefon* or notice or dispatch* or deliver* or deadline or sensitive D. control* or randomi* or blind* or mask* or trial* or compar* or experiment* or "exp" or factorial E. A and B and C and D
Social Science Citation Index 1981 ‐ 1999 Science Citation Indes 1981 ‐ 1999 [(survey* or questionnair*) and (return* or respon*)]
Social Psychological Educational Criminological Trials Register (SPECTR) 1950 ‐ 1998 EconLit 1969 ‐ 2000 Sociological Abstracts 1963 ‐ 2000
((survey$ or questionn$) and (return$ or respon$)).ti or ((survey$ or questionn$) and (mail$ or post$)).ti or ((return$ or respon$) and (mail$ or post$)).ti
Index to Scientific & Technical Proceedings 1982 ‐ 2000
((survey*, questionn*)+(return*,respon*))@TI, ((return*,respon*)+(mail,mailed,postal))@TI, ((survey*,questionn*)+(mail,mailed,postal))@TI
National Research Register (Web version): 2000.1
((survey*:ti or questionn*:ti) and (return*:ti or respon*:ti)) or ((return*:ti or respon*:ti) and (mail:ti or mailed:ti or postal:ti)) or ((survey*:ti or questionn*:ti) and (mail:ti or mailed:ti or postal:ti))
The following literature reviews and meta‐analyses were inspected for eligible trials:
Armstrong JS. Monetary incentives in mail surveys. Public Opinion Quarterly 1975;39:111‐6.
Armstrong S. Return postage in mail surveys: a meta analysis. Public Opinion Quarterly 1987;51:233‐48.
Bogen K. The effects of questionnaire length on response rates ‐ a review of the literature. American Statistical Association 1996;1020‐5.
Boser JA. Reviewing the research on mail survey response rates: descriptive study. Paper presented at the annual meeting of the American Educational Research Association New York. April 1996.
Boser JA. Factors influencing mail survey response rates: What do we really know? Paper presented at the Annual meeting of the Mid‐South Educational Research Association. November 1995.
Brehm J. Stubbing our toes for a foot in the door? Prior contact, incentives and survey response. International Journal of Public Opinion Research 1994;6(1):45‐63.
Church AH. Estimating the effect of incentives on mail survey response rates: a meta‐analysis. Public Opinion Quarterly 1993;57:62‐79.
Cox WE. Response patterns to mail surveys. Journal of Marketing Research 1966;3:392‐7.
Downs PE. Recent evidence on the relationship between anonymity and response variables for mail surveys. Journal of the Academy of Marketing Science 1986;14(1):72‐82.
Duncan WJ. Mail questionnaires in survey research: a review of response inducement techniques. Journal of Management 1979;5(1):39‐55.
Erdos PL. Visible vs. disguised keying on questionnaires. Journal of Advertising Research 1977;17(1):13‐8.
Fox RJ. Mail survey response rate. A meta‐analysis of selected techniques for inducing response. Public Opinion Quarterly 1988;52:467‐91.
Francel EG. Mail‐administered questionnaires: a success story. Journal of Marketing Research 1966;3:89‐92.
Goyder JC. Further evidence on factors affecting response rates to mailed questionnaires. American Sociological Review 1982;47:550‐3.
Green KE. Reviewing the research on mail survey response rates: a meta‐analysis. Paper presented at the Annual Meeting of the American Educational Research Association. April 1996.
Greenwald HP. Issues in survey data on medical practice: some empirical comparisons. Public Health Reports 1986;101(5):514‐46.
Guffey H. Stamps versus postal permits: a decisional guide for return postage in mail questionnaires. Journal of Academy of Marketing Science 1980;8(3): 234‐42.
Harvey L. Factors affecting response rates to mailed questionnaires: a comprehensive literature review. Journal of the Market Research Society 1987;29:341‐53.
Heberlein TA. Factors affecting response rates to mailed questionnaires. American Sociological Review 1978;43(4):447‐62.
Hopkins KD. Response rates in survey research: a meta‐analysis of the effects of monetary gratuities. Journal of Experimental Education 1992;61:52‐62.
Houston MJ. Broadening the scope of methodological research on mail surveys. Journal of Marketing Research 1976;13:397‐403.
Jobber D. Improving response rates in industrial mail surveys. Industrial Marketing Management 1986;15:183‐95.
Jobber D. Modelling the effects of prepaid monetary incentives on mail survey response. Journal of the Operational Research Society 1988;39:365‐72.
Jobber D. Questionnaire factors and mail survey response rates. European Research. 1985;(July)124‐9.
Jobber D. Maximizing response rates in industrial mail surveys: a review of the evidence. Advances in Business Marketing 1990;4:121‐46.
Kanuk L. Mail surveys and response rates: a literature review. Journal of Marketing Research 1975;12:440‐53.
King FW. Anonymous versus identifiable questionnaires in drug usage surveys. American Psychologist 1970;25:982‐5.
Leslie L. Increasing response rates to long questionnaires. Journal of Educational Research 1970;63:347‐50.
Linsky AS. Stimulating responses to mailed questionnaires: a review. Public Opinion Quarterly 1975;39:82‐101.
Mayer EN. Postage stamps do affect results of your mailing. Printers' Ink 1946;217:91.
Nowack KM. Getting them out and getting them back. Training Development Journal 1990;(April)82‐5.
Ransdell LB. Maximising response rate in questionnaire research. American Journal of Health Behaviour 1996;20:50‐6.
Robin S. A procedure for securing returns to mail questionnaires. Sociology and Social Research 1965;50:24‐35
Roth PL. Response rates in HRM/OB survey research: norms and correlates, 1990‐1994. Journal of Management 1998;24:97‐117.
Schlegelmilch BB. Prenotification and mail survey response rates: a quantitative integration of the literature. Journal of the Market Research Society 1991;33(3):243‐55.
Scott C. Research on mail surveys. Journal of the Royal Statistical Society 1961;124:143‐205.
Singer E. Confidentiality assurances and response: a quantitative review of the experimental literature. Public Opinion Quarterly 1995;59: 66‐77.
Vaux A. Conducting mail surveys. Psychology Research Handbook. 1996:(Chapter 10).
Wiseman F. A reassessment of the effects of personalization on response patterns in mail wurveys. Journal of Marketing Research 1976;3I:110‐1.
Yammarino FJ. Understanding mail survey response behaviour: a meta‐analysis. Public Opinion Quarterly 1991;55: 613‐39.
Young JM. Improving survey response rates: a meta‐analysis of the effectiveness of an advance telephone prompt from a medical peer. Medical Journal of Australia 1999;170: 339.
Yu J. A quantitative review of research design effects on response rates to questionnaires. Journal of Marketing Research 1983;XX:36‐44.
Zelnio RN. Data collection techniques: mail questionnaires. American Journal of Hospital Pharmacy 1980;37:1113‐9.
The following journals were searched by hand:
Public Opinion Quarterly 1960 to 1998 American Journal of Epidemiology 1948 to 1999
Reliability of screening for eligible trials
The electronic bibliographic searches outlined above yielded several thousand records of potentially relevant reports that were then screened to determine eligibility. Because exclusion of reports during screening would mean that they would not be considered again, we assessed the accuracy and reliability of screening for relevant trials using the records retrieved by a search of ten databases.
A search of ten electronic bibliographic databases yielded 26,937 records of potentially relevant reports that were downloaded into a ProCite database. After removing duplicate records, there were 22,571 records of potentially relevant reports. These records were divided into six approximately equal sets (A to F) and each of four reviewers was allocated three of the sets to screen. The six sets were allocated such that two reviewers examined each record and identification of trials by each reviewer could be compared with each of the other reviewers. Agreement between reviewers was assessed using Cohen's kappa statistic (k) which adjusts the proportion of records in which there was agreement between reviewers by the amount of agreement that is expected by chance alone. Ascertainment intersection (capture‐recapture) methods (Hook 1992) were then used to estimate the likely number of relevant records missed by all four reviewers. When screening was complete, full copies of the reports identified by at least one reviewer as potentially relevant were requested. Each report obtained was assessed independently by two reviewers for eligibility for inclusion in the systematic review. Disagreements about eligibility were referred to a third reviewer. Eligible reports were used as the 'gold standard' against which an assessment was made about the accuracy of screening by reviewers.
After screening, 301 of 22,571 records were identified by at least one reviewer as potentially relevant. Of the six possible comparisons between reviewers, kappa coefficients of agreement ranged from 0.59 (95% CI 0.56 to 0.62) to 0.93 (95% CI 0.90 to 0.96). Agreement was 'almost perfect' (k > 0.81) between two pairs, 'substantial' (k > 0.61) between three pairs, and 'moderate' (k > 0.41) between one pair. Ascertainment intersection methods suggest that, on average, pairs of reviewers missed 4% (range 0% to 6%) of potentially relevant records. In contrast, single reviewers missed on average 22% (range 3% to 55%). Twenty‐eight reports were not available by the time of the ascertainment intersection analysis. Of the 273 reports that were available, 156 (57%) met the inclusion criteria for the systematic review. Ascertainment intersection methods estimated that pairs of reviewers had missed very few eligible records (0 records missed, 95% CI 0 to 3 records). In the light of these results we believe that very few eligible trials were inappropriately excluded during screening.
Sensitivity of combined search strategy
The sensitivity of the search strategy was assessed by handsearching Public Opinion Quarterly and comparing the trials identified by handsearching with those identified by the combined search strategy. Of the 40 eligible trials identified by hand searching, 15 trials had been identified from electronic bibliographic databases and 23 had been identified from the reference lists of identified trials and relevant meta‐analyses. Two studies identified by handsearching were not identified by any part of the combined search strategy. On the basis of these results, electronic bibliographic database searching had a sensitivity of 38% (15/40), searching reference lists of identified trials and relevant meta‐analyses had a sensitivity of 58% (23/40), and the combined search strategy had a sensitivity of 95% (38/40), (95% CI 84% to 99%).
UPDATE OF REVIEW: 2003
In 2003 the following databases were searched again using the appropriate strategies detailed above.
Database time period or version
Cochrane Controlled Trials Register 2002.4 CINAHL 1999.07 ‐ 2003.02 ERIC 1998.09 ‐ 2003.01 PsycLit 1999.09 ‐ 2003.02 Dissertation Abstracts 1999.08 ‐ 2003.02 MEDLINE 1999 ‐ 2003 EMBASE 1999.08 ‐ 2003.02 Science Citation Index 1999 ‐ 2003 Social Science Citation Index 1999 ‐ 2003 Social Psychological Educational Criminological Trials Register (SPECTR) 1998 ‐ 2003 EconLit 2000 ‐ 2003.01 Sociological Abstracts 2000 ‐ 2002.12 Index to Scientific & Technical Proceedings 2000 ‐ 2003 National Research Register (Web version): 2003.2
A search of these databases yielded 6423 records of potentially relevant reports that were downloaded into a ProCite database. Two reviewers examined each record so that identification of trials by each reviewer could be compared. After screening, 194 of 6423 records were identified by at least one reviewer as potentially relevant.
During the update, attempts were made to obtain sufficient information on studies awaiting assessment to be able to include or exclude them from the review. This included writing to or emailing the authors of all potentially eligible trials and those in studies awaiting assessment.
UPDATE OF REVIEW: 2008
In 2008 the following databases were searched again using the appropriate strategies detailed above. The search also included electronic‐based questionnaires such as those sent via e‐mail, and online surveys.
Cochrane Library Online Issue 4 2007 CENTRAL Cochrane Library Online Issue 4 2007 Methodology studies (CMR) CINAHL 2003 ‐ 2007.12 ERIC 2003 ‐ 2007.12 PsycINFO 2003 ‐ 2008.01 MEDLINE 2003 ‐ 2007.11 EMBASE 2003 ‐ 2007.10 Science Citation Index 2003 ‐ 2008.01 Social Science Citation Index 2003 ‐ 2008.01 Social Psychological Educational Criminological Trials Register (SPECTR) 2003 ‐ 2007.12 EconLit 2003 ‐ 2007.12 Sociological Abstracts 2003 ‐ 2007.12 Dissertation & Theses 2003 ‐ 2008.01 Index to Scientific & Technical Proceedings 2003 ‐ 2008.01 National Research Register (Web version): 2008.02
A search of these databases yielded 19,826 records of potentially relevant reports that were downloaded into an EndNote database. After removing duplicates, we identified 14,792 records. Two reviewers examined each record so that identification of trials by each reviewer could be compared. After screening, 253 of 14,792 records were identified by at least one reviewer as potentially relevant and their full texts were sought.
During the update, attempts were made to obtain sufficient information on studies awaiting assessment to be able to include or exclude them from the review. This included writing to or emailing the authors of all potentially eligible trials and those studies awaiting assessment.
Appendix 2. Conversion of odds ratios to response rates from different baseline rates
| Odds ratio | 0.50 | 0.75 | 1.00 | 1.25 | 1.50 | 1.75 | 2.00 | 2.25 | 2.50 | 2.75 | 3.00 | |||||||||||||
| Baseline % | ||||||||||||||||||||||||
| 10 | 5 | 8 | 10 | 12 | 14 | 16 | 18 | 20 | 22 | 23 | 25 | |||||||||||||
| 20 | 11 | 16 | 20 | 24 | 27 | 30 | 33 | 36 | 38 | 41 | 43 | |||||||||||||
| 30 | 18 | 24 | 30 | 35 | 39 | 43 | 46 | 49 | 52 | 54 | 56 | |||||||||||||
| 40 | 25 | 33 | 40 | 45 | 50 | 54 | 57 | 60 | 63 | 65 | 67 | |||||||||||||
| 50 | 33 | 43 | 50 | 56 | 60 | 64 | 67 | 69 | 71 | 73 | 75 | |||||||||||||
| 60 | 43 | 53 | 60 | 65 | 69 | 72 | 75 | 77 | 79 | 80 | 82 | |||||||||||||
| 65 | 48 | 58 | 65 | 70 | 74 | 76 | 79 | 81 | 82 | 84 | 85 | |||||||||||||
| 70 | 54 | 64 | 70 | 74 | 78 | 80 | 82 | 84 | 85 | 87 | 88 | |||||||||||||
| 75 | 60 | 69 | 75 | 79 | 82 | 84 | 86 | 87 | 88 | 89 | 90 | |||||||||||||
| 80 | 67 | 75 | 80 | 83 | 86 | 88 | 89 | 90 | 91 | 92 | 92 | |||||||||||||
| 85 | 74 | 81 | 85 | 88 | 89 | 91 | 92 | 93 | 93 | 94 | 94 | |||||||||||||
| 90 | 82 | 87 | 90 | 92 | 93 | 94 | 95 | 95 | 96 | 96 | 96 | |||||||||||||
| 95 | 90 | 93 | 95 | 96 | 97 | 97 | 97 | 98 | 98 | 98 | 98 |
Data and analyses
Comparison 1. Monetary incentive vs. no incentive.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 56 | 61094 | Odds Ratio (M‐H, Random, 95% CI) | 2.17 [1.95, 2.41] |
| 2 Final response | 94 | 160004 | Odds Ratio (M‐H, Random, 95% CI) | 1.87 [1.73, 2.03] |
| 3 e ‐ Log | 1 | 1102 | Odds Ratio (M‐H, Random, 95% CI) | 0.99 [0.74, 1.32] |
| 4 e ‐ Submission | 1 | 1102 | Odds Ratio (M‐H, Random, 95% CI) | 1.19 [0.82, 1.75] |
1.1. Analysis.
Comparison 1 Monetary incentive vs. no incentive, Outcome 1 First response.
1.3. Analysis.
Comparison 1 Monetary incentive vs. no incentive, Outcome 3 e ‐ Log.
Comparison 2. Larger vs. smaller monetary incentive.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 13 | 12279 | Odds Ratio (M‐H, Random, 95% CI) | 1.25 [1.10, 1.41] |
| 2 Final response | 37 | 84043 | Odds Ratio (M‐H, Random, 95% CI) | 1.26 [1.14, 1.39] |
2.1. Analysis.
Comparison 2 Larger vs. smaller monetary incentive, Outcome 1 First response.
Comparison 3. Monetary vs. non‐monetary incentive.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 4 | 8650 | Odds Ratio (M‐H, Random, 95% CI) | 1.77 [1.17, 2.68] |
| 2 Final response | 13 | 26484 | Odds Ratio (M‐H, Random, 95% CI) | 1.62 [1.39, 1.88] |
| 3 e ‐ Login | 1 | 1100 | Odds Ratio (M‐H, Random, 95% CI) | 0.66 [0.50, 0.87] |
| 4 e ‐ Submission | 2 | 2856 | Odds Ratio (M‐H, Random, 95% CI) | 0.77 [0.48, 1.23] |
3.1. Analysis.
Comparison 3 Monetary vs. non‐monetary incentive, Outcome 1 First response.
3.3. Analysis.
Comparison 3 Monetary vs. non‐monetary incentive, Outcome 3 e ‐ Login.
Comparison 4. Non‐monetary incentive vs. no incentive.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 44 | 65687 | Odds Ratio (M‐H, Random, 95% CI) | 1.17 [1.08, 1.25] |
| 2 Final response | 94 | 135934 | Odds Ratio (M‐H, Random, 95% CI) | 1.15 [1.08, 1.22] |
| 3 e ‐ Login | 2 | 10035 | Odds Ratio (M‐H, Random, 95% CI) | 1.32 [1.09, 1.59] |
| 4 e ‐ Submission | 6 | 17493 | Odds Ratio (M‐H, Random, 95% CI) | 1.72 [1.09, 2.72] |
4.1. Analysis.
Comparison 4 Non‐monetary incentive vs. no incentive, Outcome 1 First response.
4.3. Analysis.
Comparison 4 Non‐monetary incentive vs. no incentive, Outcome 3 e ‐ Login.
Comparison 5. Larger non‐monetary incentive vs. smaller.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 3632 | Odds Ratio (M‐H, Random, 95% CI) | 1.18 [1.01, 1.39] |
| 2 Final response | 7 | 10730 | Odds Ratio (M‐H, Random, 95% CI) | 1.09 [0.97, 1.22] |
| 3 e ‐ Login | 1 | 7322 | Odds Ratio (M‐H, Random, 95% CI) | 1.11 [0.91, 1.35] |
| 4 e ‐ Submission | 7 | 31454 | Odds Ratio (M‐H, Random, 95% CI) | 0.95 [0.78, 1.15] |
5.1. Analysis.
Comparison 5 Larger non‐monetary incentive vs. smaller, Outcome 1 First response.
5.3. Analysis.
Comparison 5 Larger non‐monetary incentive vs. smaller, Outcome 3 e ‐ Login.
Comparison 6. Immediate notification of lottery results vs. delayed notification.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 1 | 2233 | Odds Ratio (M‐H, Random, 95% CI) | 1.37 [1.13, 1.65] |
Comparison 7. Higher denominations in monetary lottery incentives vs. lower.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 2 | 4721 | Odds Ratio (M‐H, Random, 95% CI) | 1.00 [0.87, 1.14] |
Comparison 8. Incentive with questionnaire vs. on response.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 12 | 19724 | Odds Ratio (M‐H, Random, 95% CI) | 2.00 [1.54, 2.60] |
| 2 Final response | 24 | 27569 | Odds Ratio (M‐H, Random, 95% CI) | 1.61 [1.36, 1.89] |
| 3 e ‐ Log | 1 | 736 | Odds Ratio (M‐H, Random, 95% CI) | 0.90 [0.64, 1.27] |
| 4 e ‐ Submission | 3 | 1401 | Odds Ratio (M‐H, Random, 95% CI) | 1.08 [0.77, 1.50] |
8.1. Analysis.
Comparison 8 Incentive with questionnaire vs. on response, Outcome 1 First response.
8.3. Analysis.
Comparison 8 Incentive with questionnaire vs. on response, Outcome 3 e ‐ Log.
Comparison 9. Incentive with first vs. subsequent mailing.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 7924 | Odds Ratio (M‐H, Random, 95% CI) | 2.20 [1.66, 2.92] |
| 2 Final response | 3 | 7924 | Odds Ratio (M‐H, Random, 95% CI) | 1.14 [1.02, 1.28] |
9.1. Analysis.
Comparison 9 Incentive with first vs. subsequent mailing, Outcome 1 First response.
Comparison 10. Unconditional and conditional incentives vs. conditional incentives.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 1 | 1061 | Odds Ratio (M‐H, Random, 95% CI) | 1.19 [0.92, 1.54] |
Comparison 11. Offer of survey results vs. no offer.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 7 | 11095 | Odds Ratio (M‐H, Random, 95% CI) | 1.01 [0.85, 1.20] |
| 2 Final response | 12 | 15256 | Odds Ratio (M‐H, Random, 95% CI) | 0.90 [0.76, 1.07] |
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 1 | 2332 | Odds Ratio (M‐H, Random, 95% CI) | 1.36 [1.15, 1.61] |
11.1. Analysis.
Comparison 11 Offer of survey results vs. no offer, Outcome 1 First response.
Comparison 12. Shorter vs. longer questionnaire.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 17 | 21885 | Odds Ratio (M‐H, Random, 95% CI) | 1.15 [1.02, 1.30] |
| 2 Final response | 56 | 60119 | Odds Ratio (M‐H, Random, 95% CI) | 1.64 [1.43, 1.87] |
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 2 | 7589 | Odds Ratio (M‐H, Random, 95% CI) | 1.73 [1.40, 2.13] |
12.1. Analysis.
Comparison 12 Shorter vs. longer questionnaire, Outcome 1 First response.
Comparison 13. Double postcard vs. one page.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 0.66 [0.48, 0.91] |
| 2 Final response | 1 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 0.47 [0.34, 0.66] |
13.1. Analysis.
Comparison 13 Double postcard vs. one page, Outcome 1 First response.
Comparison 14. More vs. less personalised.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 30 | 23111 | Odds Ratio (M‐H, Random, 95% CI) | 1.22 [1.09, 1.37] |
| 2 Final response | 58 | 60184 | Odds Ratio (M‐H, Random, 95% CI) | 1.14 [1.07, 1.22] |
| 3 e ‐ Login | 5 | 24557 | Odds Ratio (M‐H, Random, 95% CI) | 1.26 [1.13, 1.40] |
| 4 e ‐ Submission | 12 | 48910 | Odds Ratio (M‐H, Random, 95% CI) | 1.24 [1.17, 1.32] |
14.1. Analysis.
Comparison 14 More vs. less personalised, Outcome 1 First response.
14.3. Analysis.
Comparison 14 More vs. less personalised, Outcome 3 e ‐ Login.
Comparison 15. Hand‐written vs. typed/facsimile/scanned/printed signature on covering letter.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 590 | Odds Ratio (M‐H, Random, 95% CI) | 1.08 [0.75, 1.54] |
| 2 Final response | 14 | 15006 | Odds Ratio (M‐H, Random, 95% CI) | 1.24 [1.08, 1.41] |
15.1. Analysis.
Comparison 15 Hand‐written vs. typed/facsimile/scanned/printed signature on covering letter, Outcome 1 First response.
Comparison 16. Hand‐written address vs. computer‐printed.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 1492 | Odds Ratio (M‐H, Random, 95% CI) | 1.37 [0.95, 1.98] |
| 2 Final response | 7 | 5091 | Odds Ratio (M‐H, Random, 95% CI) | 1.25 [1.08, 1.45] |
16.1. Analysis.
Comparison 16 Hand‐written address vs. computer‐printed , Outcome 1 First response.
Comparison 17. Signed vs. unsigned.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 1030 | Odds Ratio (M‐H, Random, 95% CI) | 1.34 [0.97, 1.85] |
Comparison 18. Identifying feature on return vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 4 | 3084 | Odds Ratio (M‐H, Random, 95% CI) | 1.06 [0.68, 1.64] |
| 2 Final response | 8 | 4134 | Odds Ratio (M‐H, Random, 95% CI) | 1.12 [0.82, 1.52] |
18.1. Analysis.
Comparison 18 Identifying feature on return vs. none, Outcome 1 First response.
Comparison 19. Identifying number on return vs. other identifier.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 741 | Odds Ratio (M‐H, Random, 95% CI) | 1.00 [0.68, 1.46] |
| 2 Final response | 1 | 741 | Odds Ratio (M‐H, Random, 95% CI) | 1.00 [0.68, 1.46] |
19.1. Analysis.
Comparison 19 Identifying number on return vs. other identifier, Outcome 1 First response.
19.2. Analysis.
Comparison 19 Identifying number on return vs. other identifier, Outcome 2 Final response.
Comparison 20. Brown vs. white envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 5423 | Odds Ratio (M‐H, Random, 95% CI) | 1.44 [0.73, 2.83] |
| 2 Final response | 5 | 8637 | Odds Ratio (M‐H, Random, 95% CI) | 1.23 [0.81, 1.87] |
20.1. Analysis.
Comparison 20 Brown vs. white envelope, Outcome 1 First response.
Comparison 21. Coloured vs. white questionnaire.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 6 | 14005 | Odds Ratio (M‐H, Random, 95% CI) | 1.07 [0.99, 1.15] |
| 2 Final response | 14 | 41421 | Odds Ratio (M‐H, Random, 95% CI) | 1.04 [0.99, 1.10] |
21.1. Analysis.
Comparison 21 Coloured vs. white questionnaire, Outcome 1 First response.
Comparison 22. Coloured vs. standard (black/blue) ink.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 6064 | Odds Ratio (M‐H, Random, 95% CI) | 1.25 [1.03, 1.53] |
| 2 Final response | 3 | 7040 | Odds Ratio (M‐H, Random, 95% CI) | 1.16 [0.95, 1.42] |
22.1. Analysis.
Comparison 22 Coloured vs. standard (black/blue) ink, Outcome 1 First response.
Comparison 23. Coloured vs. black & white letterhead.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 1650 | Odds Ratio (M‐H, Random, 95% CI) | 0.99 [0.80, 1.24] |
| 2 Final response | 2 | 2356 | Odds Ratio (M‐H, Random, 95% CI) | 1.08 [0.91, 1.28] |
23.1. Analysis.
Comparison 23 Coloured vs. black & white letterhead, Outcome 1 First response.
Comparison 24. Illustration on cover of q'aire largely in black vs. largely in white.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 320 | Odds Ratio (M‐H, Random, 95% CI) | 1.62 [1.04, 2.53] |
Comparison 25. Folder or booklet vs. stapled pages.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 1845 | Odds Ratio (M‐H, Random, 95% CI) | 1.17 [0.94, 1.45] |
| 2 Final response | 3 | 5681 | Odds Ratio (M‐H, Random, 95% CI) | 1.10 [0.99, 1.23] |
25.1. Analysis.
Comparison 25 Folder or booklet vs. stapled pages, Outcome 1 First response.
Comparison 26. Large paper size vs. small.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 2000 | Odds Ratio (M‐H, Random, 95% CI) | 0.88 [0.71, 1.09] |
| 2 Final response | 2 | 2145 | Odds Ratio (M‐H, Random, 95% CI) | 0.88 [0.56, 1.39] |
26.1. Analysis.
Comparison 26 Large paper size vs. small, Outcome 1 First response.
Comparison 27. Dot matrix print vs. letter quality print.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 176 | Odds Ratio (M‐H, Random, 95% CI) | 1.15 [0.63, 2.10] |
Comparison 28. Questionnaire printed on high vs. standard quality paper or thick paper vs. thin.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 1039 | Odds Ratio (M‐H, Random, 95% CI) | 0.80 [0.60, 1.06] |
Comparison 29. Single vs. double‐sided questionnaire.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 608 | Odds Ratio (M‐H, Random, 95% CI) | 1.34 [0.96, 1.87] |
| 2 Final response | 4 | 4966 | Odds Ratio (M‐H, Random, 95% CI) | 1.22 [1.01, 1.47] |
29.1. Analysis.
Comparison 29 Single vs. double‐sided questionnaire, Outcome 1 First response.
Comparison 30. Large font size vs. small.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 650 | Odds Ratio (M‐H, Random, 95% CI) | 1.26 [0.87, 1.82] |
Comparison 31. Study logo on several items in the mailing package vs. on questionnaire only.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 1000 | Odds Ratio (M‐H, Random, 95% CI) | 0.92 [0.72, 1.18] |
Comparison 32. Picture of researcher/images vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 384 | Odds Ratio (M‐H, Random, 95% CI) | 0.98 [0.61, 1.58] |
| 2 Final response | 4 | 3710 | Odds Ratio (M‐H, Random, 95% CI) | 1.07 [0.76, 1.53] |
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 2 | 720 | Odds Ratio (M‐H, Random, 95% CI) | 3.05 [1.84, 5.06] |
32.1. Analysis.
Comparison 32 Picture of researcher/images vs. none, Outcome 1 First response.
Comparison 33. Attractive vs. less attractive picture.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 2 | 520 | Odds Ratio (M‐H, Random, 95% CI) | 3.44 [0.72, 16.49] |
Comparison 34. Cartoons included vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 280 | Odds Ratio (M‐H, Random, 95% CI) | 1.0 [0.62, 1.62] |
Comparison 35. Matrix vs. standard form.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 316 | Odds Ratio (M‐H, Random, 95% CI) | 0.61 [0.32, 1.19] |
| 2 Final response | 2 | 316 | Odds Ratio (M‐H, Random, 95% CI) | 0.58 [0.29, 1.16] |
35.1. Analysis.
Comparison 35 Matrix vs. standard form, Outcome 1 First response.
Comparison 36. Questions ordered by time period vs. other order.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 2 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 3 Final response | 1 | 259 | Odds Ratio (M‐H, Random, 95% CI) | 1.48 [0.84, 2.59] |
Comparison 37. Subject line vs. blank.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 e ‐ Login | 2 | 6152 | Odds Ratio (M‐H, Fixed, 95% CI) | 0.84 [0.71, 0.99] |
| 2 e ‐ Submission | 2 | 6152 | Odds Ratio (M‐H, Fixed, 95% CI) | 0.84 [0.71, 1.01] |
37.1. Analysis.
Comparison 37 Subject line vs. blank, Outcome 1 e ‐ Login.
Comparison 38. "Survey" subject line vs. blank.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 e ‐ Login | 2 | 3845 | Odds Ratio (M‐H, Random, 95% CI) | 0.80 [0.67, 0.97] |
| 2 e ‐ Submission | 2 | 3845 | Odds Ratio (M‐H, Random, 95% CI) | 0.81 [0.67, 0.97] |
38.1. Analysis.
Comparison 38 "Survey" subject line vs. blank, Outcome 1 e ‐ Login.
Comparison 39. Text vs. HTML file formats.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 e ‐ Submission | 1 | 6090 | Odds Ratio (M‐H, Random, 95% CI) | 1.0 [0.84, 1.19] |
Comparison 40. White background vs. black.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 e ‐ Submission | 1 | 6090 | Odds Ratio (M‐H, Random, 95% CI) | 1.31 [1.10, 1.56] |
Comparison 41. Header vs. no header.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 e ‐ Submission | 1 | 6090 | Odds Ratio (M‐H, Random, 95% CI) | 1.13 [0.90, 1.41] |
Comparison 42. Simple vs. complex header.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 e ‐ Submission | 1 | 5075 | Odds Ratio (M‐H, Random, 95% CI) | 1.23 [1.03, 1.48] |
Comparison 43. Textual presentation of response categories vs. visual presentation.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 1 | 5413 | Odds Ratio (M‐H, Random, 95% CI) | 1.19 [1.05, 1.36] |
Comparison 44. Stamped vs. franked outward envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 930 | Odds Ratio (M‐H, Random, 95% CI) | 1.04 [0.79, 1.37] |
| 2 Final response | 6 | 13964 | Odds Ratio (M‐H, Random, 95% CI) | 0.95 [0.88, 1.03] |
44.1. Analysis.
Comparison 44 Stamped vs. franked outward envelope, Outcome 1 First response.
Comparison 45. First vs. second/third class outward mailing.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 7370 | Odds Ratio (M‐H, Random, 95% CI) | 1.12 [1.02, 1.23] |
| 2 Final response | 2 | 8300 | Odds Ratio (M‐H, Random, 95% CI) | 1.11 [1.02, 1.21] |
45.1. Analysis.
Comparison 45 First vs. second/third class outward mailing, Outcome 1 First response.
Comparison 46. Commemorative/race‐specific vs. ordinary stamp on return envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 2430 | Odds Ratio (M‐H, Random, 95% CI) | 0.91 [0.66, 1.24] |
| 2 Final response | 5 | 5461 | Odds Ratio (M‐H, Random, 95% CI) | 0.92 [0.81, 1.06] |
46.1. Analysis.
Comparison 46 Commemorative/race‐specific vs. ordinary stamp on return envelope, Outcome 1 First response.
Comparison 47. Certified/special delivery vs. regular outward mailing.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 9 | 15193 | Odds Ratio (M‐H, Random, 95% CI) | 2.32 [1.55, 3.46] |
| 2 Final response | 15 | 18931 | Odds Ratio (M‐H, Random, 95% CI) | 1.76 [1.43, 2.18] |
47.1. Analysis.
Comparison 47 Certified/special delivery vs. regular outward mailing, Outcome 1 First response.
Comparison 48. Stamped vs. business reply/franked return envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 15 | 27234 | Odds Ratio (M‐H, Random, 95% CI) | 1.24 [1.12, 1.36] |
| 2 Final response | 27 | 48612 | Odds Ratio (M‐H, Random, 95% CI) | 1.24 [1.14, 1.35] |
48.1. Analysis.
Comparison 48 Stamped vs. business reply/franked return envelope, Outcome 1 First response.
Comparison 49. Priority stamps vs. first‐class stamps on return envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 205 | Odds Ratio (M‐H, Random, 95% CI) | 0.26 [0.14, 0.46] |
Comparison 50. First vs. second class stamp on return envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 800 | Odds Ratio (M‐H, Random, 95% CI) | 0.91 [0.69, 1.21] |
Comparison 51. Multiple stamps vs. single stamp on return envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 510 | Odds Ratio (M‐H, Random, 95% CI) | 1.44 [1.01, 2.04] |
Comparison 52. Questionnaire sent to work vs. home address.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 1140 | Odds Ratio (M‐H, Random, 95% CI) | 1.16 [0.89, 1.52] |
| 2 Final response | 2 | 1140 | Odds Ratio (M‐H, Random, 95% CI) | 1.16 [0.89, 1.52] |
52.1. Analysis.
Comparison 52 Questionnaire sent to work vs. home address, Outcome 1 First response.
Comparison 53. Pre‐paid return envelope vs. not pre‐paid.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 2740 | Odds Ratio (M‐H, Random, 95% CI) | 1.23 [0.78, 1.95] |
| 2 Final response | 4 | 4094 | Odds Ratio (M‐H, Random, 95% CI) | 1.09 [0.71, 1.68] |
53.1. Analysis.
Comparison 53 Pre‐paid return envelope vs. not pre‐paid, Outcome 1 First response.
Comparison 54. Stamped addressed return envelope vs. address label only included.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 147 | Odds Ratio (M‐H, Random, 95% CI) | 0.86 [0.45, 1.65] |
Comparison 55. Q'aire mailed in large vs. standard/small envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 1200 | Odds Ratio (M‐H, Random, 95% CI) | 0.93 [0.74, 1.17] |
Comparison 56. Window vs. regular envelope.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 11781 | Odds Ratio (M‐H, Random, 95% CI) | 0.85 [0.68, 1.06] |
| 2 Final response | 2 | 11781 | Odds Ratio (M‐H, Random, 95% CI) | 0.96 [0.61, 1.49] |
56.1. Analysis.
Comparison 56 Window vs. regular envelope, Outcome 1 First response.
Comparison 57. Postal + optional Internet response vs. only postal response.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 4213 | Odds Ratio (M‐H, Random, 95% CI) | 0.99 [0.87, 1.13] |
| 2 Final response | 1 | 4213 | Odds Ratio (M‐H, Random, 95% CI) | 0.93 [0.82, 1.05] |
57.1. Analysis.
Comparison 57 Postal + optional Internet response vs. only postal response, Outcome 1 First response.
Comparison 58. Questionnaire mailed on Monday vs. Friday.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 504 | Odds Ratio (M‐H, Random, 95% CI) | 0.83 [0.58, 1.17] |
| 2 Final response | 1 | 504 | Odds Ratio (M‐H, Random, 95% CI) | 0.83 [0.58, 1.17] |
58.1. Analysis.
Comparison 58 Questionnaire mailed on Monday vs. Friday, Outcome 1 First response.
Comparison 59. Questionnaire received on Monday vs. Friday.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 460 | Odds Ratio (M‐H, Random, 95% CI) | 1.0 [0.64, 1.56] |
Comparison 60. Q'aire sent 1‐5 weeks vs. 9‐14 weeks after hospital discharge.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 2324 | Odds Ratio (M‐H, Random, 95% CI) | 2.26 [0.69, 7.37] |
Comparison 61. Pre‐contact vs. no pre‐contact.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 24 | 49019 | Odds Ratio (M‐H, Random, 95% CI) | 1.50 [1.26, 1.78] |
| 2 Final response | 47 | 79651 | Odds Ratio (M‐H, Random, 95% CI) | 1.45 [1.29, 1.63] |
61.1. Analysis.
Comparison 61 Pre‐contact vs. no pre‐contact, Outcome 1 First response.
Comparison 62. Pre‐contact by phone vs. mail.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 978 | Odds Ratio (M‐H, Random, 95% CI) | 1.40 [1.02, 1.93] |
| 2 Final response | 7 | 3322 | Odds Ratio (M‐H, Random, 95% CI) | 1.18 [0.77, 1.80] |
62.1. Analysis.
Comparison 62 Pre‐contact by phone vs. mail, Outcome 1 First response.
Comparison 63. Follow up vs. no follow up.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 10 | 10738 | Odds Ratio (M‐H, Random, 95% CI) | 1.56 [1.22, 2.00] |
| 2 Final response | 19 | 32778 | Odds Ratio (M‐H, Random, 95% CI) | 1.35 [1.18, 1.55] |
63.1. Analysis.
Comparison 63 Follow up vs. no follow up, Outcome 1 First response.
Comparison 64. Postal follow‐up including vs. excluding q'aire.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 6 | 5261 | Odds Ratio (M‐H, Random, 95% CI) | 1.20 [0.89, 1.61] |
| 2 Final response | 11 | 8619 | Odds Ratio (M‐H, Random, 95% CI) | 1.46 [1.13, 1.90] |
64.1. Analysis.
Comparison 64 Postal follow‐up including vs. excluding q'aire, Outcome 1 First response.
Comparison 65. Follow up by phone vs. mail.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First Response | 4 | 1198 | Odds Ratio (M‐H, Random, 95% CI) | 0.67 [0.46, 0.97] |
| 2 Final Response | 5 | 2254 | Odds Ratio (M‐H, Random, 95% CI) | 0.86 [0.54, 1.36] |
65.1. Analysis.
Comparison 65 Follow up by phone vs. mail, Outcome 1 First Response.
Comparison 66. Telephone reminder vs. no reminder.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 143 | Odds Ratio (M‐H, Random, 95% CI) | 4.29 [1.70, 10.81] |
| 2 Final response | 3 | 13922 | Odds Ratio (M‐H, Random, 95% CI) | 1.29 [0.85, 1.96] |
66.1. Analysis.
Comparison 66 Telephone reminder vs. no reminder, Outcome 1 First response.
Comparison 67. SMS vs. postcard reminder.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 3 | 9947 | Odds Ratio (M‐H, Random, 95% CI) | 1.49 [1.23, 1.81] |
Comparison 68. Follow‐up interval < 31 days vs. 31‐60 days.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 1608 | Odds Ratio (M‐H, Random, 95% CI) | 0.87 [0.50, 1.50] |
| 2 Final response | 2 | 1608 | Odds Ratio (M‐H, Random, 95% CI) | 0.97 [0.75, 1.26] |
68.1. Analysis.
Comparison 68 Follow‐up interval < 31 days vs. 31‐60 days, Outcome 1 First response.
Comparison 69. Sensitive questions vs. no/fewer/less sensitive questions asked.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 5 | 11292 | Odds Ratio (M‐H, Random, 95% CI) | 0.98 [0.90, 1.07] |
| 2 Final response | 10 | 21393 | Odds Ratio (M‐H, Random, 95% CI) | 0.94 [0.88, 1.00] |
69.1. Analysis.
Comparison 69 Sensitive questions vs. no/fewer/less sensitive questions asked, Outcome 1 First response.
Comparison 70. More relevant questions first vs. last.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 5817 | Odds Ratio (M‐H, Random, 95% CI) | 1.28 [1.15, 1.42] |
| 2 Final response | 1 | 5817 | Odds Ratio (M‐H, Random, 95% CI) | 1.23 [1.10, 1.37] |
70.1. Analysis.
Comparison 70 More relevant questions first vs. last, Outcome 1 First response.
Comparison 71. Most general question first vs. last.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 3 | 11435 | Odds Ratio (M‐H, Random, 95% CI) | 0.95 [0.83, 1.09] |
Comparison 72. Demographic items first vs. last.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 1040 | Odds Ratio (M‐H, Random, 95% CI) | 1.06 [0.83, 1.36] |
| 2 Final response | 4 | 3598 | Odds Ratio (M‐H, Random, 95% CI) | 1.08 [0.94, 1.25] |
72.1. Analysis.
Comparison 72 Demographic items first vs. last, Outcome 1 First response.
Comparison 73. Easier questions first vs. last.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 240 | Odds Ratio (M‐H, Random, 95% CI) | 1.80 [0.91, 3.56] |
| 2 Final response | 2 | 3182 | Odds Ratio (M‐H, Random, 95% CI) | 1.61 [1.14, 2.26] |
73.1. Analysis.
Comparison 73 Easier questions first vs. last, Outcome 1 First response.
Comparison 74. User friendly vs. standard questionnaire.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 3540 | Odds Ratio (M‐H, Random, 95% CI) | 1.46 [1.21, 1.75] |
| 2 Final response | 1 | 3540 | Odds Ratio (M‐H, Random, 95% CI) | 1.46 [1.21, 1.75] |
74.1. Analysis.
Comparison 74 User friendly vs. standard questionnaire, Outcome 1 First response.
Comparison 75. More interesting vs. less or high salient topic vs. low.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 2151 | Odds Ratio (M‐H, Random, 95% CI) | 2.44 [1.99, 3.01] |
| 2 Final response | 3 | 2711 | Odds Ratio (M‐H, Random, 95% CI) | 2.00 [1.32, 3.04] |
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Fixed, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 1 | 2176 | Odds Ratio (M‐H, Fixed, 95% CI) | 1.85 [1.52, 2.26] |
75.1. Analysis.
Comparison 75 More interesting vs. less or high salient topic vs. low, Outcome 1 First response.
Comparison 76. Open‐ended vs. closed questions.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 372 | Odds Ratio (M‐H, Random, 95% CI) | 0.38 [0.25, 0.59] |
| 2 Final response | 3 | 1764 | Odds Ratio (M‐H, Random, 95% CI) | 0.31 [0.09, 1.04] |
76.1. Analysis.
Comparison 76 Open‐ended vs. closed questions, Outcome 1 First response.
Comparison 77. Open‐ended items first vs. other items first.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 300 | Odds Ratio (M‐H, Random, 95% CI) | 0.89 [0.55, 1.44] |
| 2 Final response | 1 | 300 | Odds Ratio (M‐H, Random, 95% CI) | 1.26 [0.73, 2.19] |
77.1. Analysis.
Comparison 77 Open‐ended items first vs. other items first, Outcome 1 First response.
Comparison 78. Closed‐ended items first vs. other items first.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 300 | Odds Ratio (M‐H, Random, 95% CI) | 1.15 [0.71, 1.86] |
| 2 Final response | 1 | 300 | Odds Ratio (M‐H, Random, 95% CI) | 0.93 [0.54, 1.59] |
78.1. Analysis.
Comparison 78 Closed‐ended items first vs. other items first, Outcome 1 First response.
Comparison 79. 'Don't know' boxes included vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 1360 | Odds Ratio (M‐H, Random, 95% CI) | 1.03 [0.82, 1.29] |
Comparison 80. Circle answer vs. tick box format.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 1125 | Odds Ratio (M‐H, Random, 95% CI) | 0.96 [0.74, 1.26] |
Comparison 81. Response options listed in increasing vs. decreasing order.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 6783 | Odds Ratio (M‐H, Random, 95% CI) | 1.06 [0.94, 1.18] |
Comparison 82. High vs. medium frequency response alternatives.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 3882 | Odds Ratio (M‐H, Random, 95% CI) | 1.40 [0.58, 3.38] |
Comparison 83. 5‐step vs. 10‐step response scale.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 654 | Odds Ratio (M‐H, Random, 95% CI) | 0.78 [0.52, 1.19] |
Comparison 84. Check categories or specify numbers vs. check categories only.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 740 | Odds Ratio (M‐H, Random, 95% CI) | 0.80 [0.60, 1.06] |
| 2 Final response | 1 | 740 | Odds Ratio (M‐H, Random, 95% CI) | 0.80 [0.60, 1.06] |
84.1. Analysis.
Comparison 84 Check categories or specify numbers vs. check categories only, Outcome 1 First response.
84.2. Analysis.
Comparison 84 Check categories or specify numbers vs. check categories only, Outcome 2 Final response.
Comparison 85. Individual item vs. stem & leaf format.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 1500 | Odds Ratio (M‐H, Random, 95% CI) | 0.88 [0.70, 1.10] |
Comparison 86. Horizontal vs. vertical orientation of response options.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 400 | Odds Ratio (M‐H, Random, 95% CI) | 3.12 [1.63, 5.96] |
Comparison 87. Conventional vs. randomised response technique.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 5830 | Odds Ratio (M‐H, Random, 95% CI) | 1.89 [1.69, 2.11] |
| 2 Final response | 4 | 7345 | Odds Ratio (M‐H, Random, 95% CI) | 1.52 [0.85, 2.72] |
87.1. Analysis.
Comparison 87 Conventional vs. randomised response technique, Outcome 1 First response.
Comparison 88. Factual questions only vs. factual and attitudinal questions.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 1280 | Odds Ratio (M‐H, Random, 95% CI) | 1.34 [1.01, 1.77] |
Comparison 89. Teaser on envelope vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 190 | Odds Ratio (M‐H, Random, 95% CI) | 3.08 [1.27, 7.44] |
| 2 Final response | 1 | 190 | Odds Ratio (M‐H, Random, 95% CI) | 3.08 [1.27, 7.44] |
89.1. Analysis.
Comparison 89 Teaser on envelope vs. none, Outcome 1 First response.
Comparison 90. Questionnaire sent with supplement vs. alone.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 1795 | Odds Ratio (M‐H, Random, 95% CI) | 0.86 [0.70, 1.07] |
Comparison 91. Extra questionnaire for relatives included vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 4943 | Odds Ratio (M‐H, Random, 95% CI) | 0.67 [0.60, 0.76] |
Comparison 92. Consent form included vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 414 | Odds Ratio (M‐H, Random, 95% CI) | 1.21 [0.81, 1.81] |
| 2 Final response | 1 | 414 | Odds Ratio (M‐H, Random, 95% CI) | 1.32 [0.89, 1.95] |
92.1. Analysis.
Comparison 92 Consent form included vs. not, Outcome 1 First response.
Comparison 93. Multi‐option vs. standard consent form.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 200 | Odds Ratio (M‐H, Random, 95% CI) | 0.91 [0.49, 1.68] |
Comparison 94. University sponsor/source vs. other.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 4 | 5241 | Odds Ratio (M‐H, Random, 95% CI) | 1.35 [0.88, 2.08] |
| 2 Final response | 14 | 21628 | Odds Ratio (M‐H, Random, 95% CI) | 1.32 [1.13, 1.54] |
| 3 e ‐ Login | 2 | 3845 | Odds Ratio (M‐H, Random, 95% CI) | 0.80 [0.67, 0.96] |
| 4 e ‐ Submission | 2 | 3845 | Odds Ratio (M‐H, Random, 95% CI) | 0.84 [0.69, 1.01] |
94.1. Analysis.
Comparison 94 University sponsor/source vs. other, Outcome 1 First response.
94.3. Analysis.
Comparison 94 University sponsor/source vs. other, Outcome 3 e ‐ Login.
Comparison 95. Sent or signed by more vs. less senior/well‐known person.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 1484 | Odds Ratio (M‐H, Random, 95% CI) | 1.06 [0.85, 1.31] |
| 2 Final response | 10 | 5644 | Odds Ratio (M‐H, Random, 95% CI) | 1.05 [0.89, 1.23] |
| 3 e ‐ Login | 1 | 17346 | Odds Ratio (M‐H, Random, 95% CI) | 0.98 [0.91, 1.06] |
| 4 e ‐ Submission | 3 | 23027 | Odds Ratio (M‐H, Random, 95% CI) | 1.05 [0.95, 1.15] |
95.1. Analysis.
Comparison 95 Sent or signed by more vs. less senior/well‐known person, Outcome 1 First response.
95.3. Analysis.
Comparison 95 Sent or signed by more vs. less senior/well‐known person, Outcome 3 e ‐ Login.
Comparison 96. University printed envelope vs. plain.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 500 | Odds Ratio (M‐H, Random, 95% CI) | 1.10 [0.77, 1.57] |
| 2 Final response | 1 | 500 | Odds Ratio (M‐H, Random, 95% CI) | 0.88 [0.61, 1.28] |
96.1. Analysis.
Comparison 96 University printed envelope vs. plain, Outcome 1 First response.
Comparison 97. Pre‐contact by medical researcher vs. non medical researcher.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 924 | Odds Ratio (M‐H, Random, 95% CI) | 1.01 [0.55, 1.86] |
Comparison 98. Q'aire sent by GP vs. by research group.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 409 | Odds Ratio (M‐H, Random, 95% CI) | 1.49 [1.00, 2.24] |
| 2 Final response | 2 | 1106 | Odds Ratio (M‐H, Random, 95% CI) | 1.52 [0.73, 3.15] |
98.1. Analysis.
Comparison 98 Q'aire sent by GP vs. by research group, Outcome 1 First response.
Comparison 99. Ethnically unidentifiable/white vs. other name.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 1.12 [0.79, 1.59] |
| 2 Final response | 5 | 5959 | Odds Ratio (M‐H, Random, 95% CI) | 1.07 [0.90, 1.27] |
99.1. Analysis.
Comparison 99 Ethnically unidentifiable/white vs. other name, Outcome 1 First response.
Comparison 100. Male vs. female investigator or male vs. female signature.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 204 | Odds Ratio (M‐H, Random, 95% CI) | 1.42 [0.76, 2.64] |
| 2 Final response | 2 | 3146 | Odds Ratio (M‐H, Random, 95% CI) | 1.07 [0.72, 1.58] |
| 3 e ‐ Login | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 4 e ‐ Submission | 2 | 720 | Odds Ratio (M‐H, Random, 95% CI) | 0.55 [0.38, 0.80] |
100.1. Analysis.
Comparison 100 Male vs. female investigator or male vs. female signature, Outcome 1 First response.
Comparison 101. Assurance of confidentiality vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 25000 | Odds Ratio (M‐H, Random, 95% CI) | 1.33 [1.24, 1.42] |
Comparison 102. Included statement that others had responded vs. no statement.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 468 | Odds Ratio (M‐H, Random, 95% CI) | 1.12 [0.76, 1.65] |
| 2 Final response | 1 | 468 | Odds Ratio (M‐H, Random, 95% CI) | 1.12 [0.76, 1.65] |
| 3 e ‐ Login | 1 | 8586 | Odds Ratio (M‐H, Random, 95% CI) | 1.41 [1.28, 1.56] |
| 4 e ‐ Submission | 1 | 8586 | Odds Ratio (M‐H, Random, 95% CI) | 1.52 [1.36, 1.70] |
102.1. Analysis.
Comparison 102 Included statement that others had responded vs. no statement, Outcome 1 First response.
102.3. Analysis.
Comparison 102 Included statement that others had responded vs. no statement, Outcome 3 e ‐ Login.
Comparison 103. Choice to opt‐out from study vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 515 | Odds Ratio (M‐H, Random, 95% CI) | 1.10 [0.77, 1.56] |
| 2 Final response | 4 | 3555 | Odds Ratio (M‐H, Random, 95% CI) | 0.92 [0.66, 1.28] |
103.1. Analysis.
Comparison 103 Choice to opt‐out from study vs. none, Outcome 1 First response.
Comparison 104. Instructions given vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 2000 | Odds Ratio (M‐H, Random, 95% CI) | 0.89 [0.74, 1.06] |
Comparison 105. Response deadline given vs. no deadline.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 2575 | Odds Ratio (M‐H, Random, 95% CI) | 1.25 [0.93, 1.69] |
| 2 Final response | 6 | 5661 | Odds Ratio (M‐H, Random, 95% CI) | 1.00 [0.84, 1.19] |
| 3 e ‐ Login | 1 | 8586 | Odds Ratio (M‐H, Random, 95% CI) | 1.20 [1.07, 1.35] |
| 4 e ‐ Submission | 1 | 8586 | Odds Ratio (M‐H, Random, 95% CI) | 1.18 [1.03, 1.34] |
105.1. Analysis.
Comparison 105 Response deadline given vs. no deadline, Outcome 1 First response.
105.3. Analysis.
Comparison 105 Response deadline given vs. no deadline, Outcome 3 e ‐ Login.
Comparison 106. Mention of obligation to respond vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 1.61 [1.16, 2.22] |
| 2 Final response | 3 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 1.61 [1.16, 2.22] |
106.1. Analysis.
Comparison 106 Mention of obligation to respond vs. none, Outcome 1 First response.
Comparison 107. Request for telephone number vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 702 | Odds Ratio (M‐H, Random, 95% CI) | 1.0 [0.65, 1.54] |
| 2 Final response | 1 | 702 | Odds Ratio (M‐H, Random, 95% CI) | 1.0 [0.65, 1.54] |
107.1. Analysis.
Comparison 107 Request for telephone number vs. none, Outcome 1 First response.
Comparison 108. Respond on questionnaire vs. on separate form.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 200 | Odds Ratio (M‐H, Random, 95% CI) | 1.11 [0.59, 2.07] |
| 2 Final response | 1 | 200 | Odds Ratio (M‐H, Random, 95% CI) | 1.13 [0.57, 2.27] |
108.1. Analysis.
Comparison 108 Respond on questionnaire vs. on separate form, Outcome 1 First response.
Comparison 109. Mention of follow‐up contact vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 5 | 4553 | Odds Ratio (M‐H, Random, 95% CI) | 1.16 [1.02, 1.33] |
| 2 Final response | 7 | 7053 | Odds Ratio (M‐H, Random, 95% CI) | 1.02 [0.91, 1.15] |
109.1. Analysis.
Comparison 109 Mention of follow‐up contact vs. none, Outcome 1 First response.
Comparison 110. Explanation for non‐participation requested vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 667 | Odds Ratio (M‐H, Random, 95% CI) | 0.97 [0.71, 1.32] |
| 2 Final response | 2 | 1907 | Odds Ratio (M‐H, Random, 95% CI) | 1.14 [0.83, 1.57] |
110.1. Analysis.
Comparison 110 Explanation for non‐participation requested vs. not, Outcome 1 First response.
Comparison 111. Time estimate for completion given vs. not.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 1.10 [0.76, 1.58] |
| 2 Final response | 1 | 600 | Odds Ratio (M‐H, Random, 95% CI) | 1.10 [0.76, 1.58] |
111.1. Analysis.
Comparison 111 Time estimate for completion given vs. not, Outcome 1 First response.
Comparison 112. Detailed vs. brief cover letter.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 500 | Odds Ratio (M‐H, Random, 95% CI) | 1.08 [0.74, 1.58] |
Comparison 113. Appeal vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 1251 | Odds Ratio (M‐H, Random, 95% CI) | 1.06 [0.79, 1.42] |
| 3 e ‐ Login | 2 | 3845 | Odds Ratio (M‐H, Random, 95% CI) | 0.85 [0.71, 1.02] |
| 4 e ‐ Submission | 2 | 3844 | Odds Ratio (M‐H, Random, 95% CI) | 0.84 [0.70, 1.01] |
113.3. Analysis.
Comparison 113 Appeal vs. none, Outcome 3 e ‐ Login.
Comparison 114. Note requesting not to remove ID code vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 100 | Odds Ratio (M‐H, Random, 95% CI) | 0.37 [0.14, 0.96] |
| 2 Final response | 1 | 100 | Odds Ratio (M‐H, Random, 95% CI) | 0.37 [0.14, 0.96] |
114.1. Analysis.
Comparison 114 Note requesting not to remove ID code vs. none, Outcome 1 First response.
Comparison 115. Request for participant signature vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 1 | 201 | Odds Ratio (M‐H, Random, 95% CI) | 1.19 [0.65, 2.18] |
Comparison 116. Questionnaire endorsed vs. not endorsed.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 395 | Odds Ratio (M‐H, Random, 95% CI) | 0.33 [0.15, 0.74] |
| 2 Final response | 1 | 395 | Odds Ratio (M‐H, Random, 95% CI) | 0.63 [0.43, 0.94] |
116.1. Analysis.
Comparison 116 Questionnaire endorsed vs. not endorsed, Outcome 1 First response.
Comparison 117. Veiled threat in follow‐up letter vs. none.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 671 | Odds Ratio (M‐H, Random, 95% CI) | 2.09 [1.49, 2.93] |
| 2 Final response | 1 | 671 | Odds Ratio (M‐H, Random, 95% CI) | 2.09 [1.49, 2.93] |
117.1. Analysis.
Comparison 117 Veiled threat in follow‐up letter vs. none, Outcome 1 First response.
Comparison 118. Appeal stresses benefit to sponsor vs. other.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 3 | 2376 | Odds Ratio (M‐H, Random, 95% CI) | 1.20 [0.88, 1.63] |
| 2 Final response | 8 | 10908 | Odds Ratio (M‐H, Random, 95% CI) | 0.99 [0.86, 1.13] |
118.1. Analysis.
Comparison 118 Appeal stresses benefit to sponsor vs. other, Outcome 1 First response.
Comparison 119. Appeal stresses benefit to respondent vs. other.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 1 | 1500 | Odds Ratio (M‐H, Random, 95% CI) | 0.97 [0.78, 1.21] |
| 2 Final response | 9 | 13175 | Odds Ratio (M‐H, Random, 95% CI) | 0.98 [0.82, 1.16] |
119.1. Analysis.
Comparison 119 Appeal stresses benefit to respondent vs. other, Outcome 1 First response.
Comparison 120. Appeal stresses benefit to society vs. other.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 2 | 1956 | Odds Ratio (M‐H, Random, 95% CI) | 0.91 [0.59, 1.40] |
| 2 Final response | 10 | 12731 | Odds Ratio (M‐H, Random, 95% CI) | 1.09 [0.92, 1.29] |
120.1. Analysis.
Comparison 120 Appeal stresses benefit to society vs. other, Outcome 1 First response.
Comparison 121. Anonymous vs. not anonymous.
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
|---|---|---|---|---|
| 1 First response | 0 | 0 | Odds Ratio (M‐H, Random, 95% CI) | 0.0 [0.0, 0.0] |
| 2 Final response | 2 | 2070 | Odds Ratio (M‐H, Random, 95% CI) | 0.96 [0.66, 1.39] |
Characteristics of studies
Characteristics of included studies [ordered by study ID]
Aadahl 2003.
| Methods | Random allocation: random numbers using SAS | |
| Data | Random sample of 2543 men and women from the Danish Civil Registration System (Copenhagen County, Denmark) | |
| Comparisons | 1. Lottery (25 euro voucher) 2. Control |
|
| Outcomes | Response at 4 weeks | |
| Topic | Health: Self‐rated health, physical activity, and socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | Mean age: 40.5 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Adams 1982.
| Methods | Random allocation: method not specified | |
| Data | Full‐time students (Brigham Young University, US) | |
| Comparisons | 1. 1‐page questionnaire 2. 3‐ page questionnaire 3. 5‐ page questionnaire | |
| Outcomes | Response at 3 months | |
| Topic | Non‐health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Albaum 1987.
| Methods | Random allocation: method not specified | |
| Data | Members of a public employees credit | |
| Comparisons | 1. University source; Open code
2. Research firm source; Open code
3. Credit union source; Open code
4. University source; No code
5. Research firm source; No code
6. Credit union source; No code Mailed reminder notification and follow up |
|
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Albaum 1989.
| Methods | Random allocation: method not specified | |
| Data | Marketing managers of manufacturing firms (Denmark) | |
| Comparisons | 1. Pre‐contact by letter; Brochure explaining the study in depth 2. Pre‐contact; No brochure 3. No pre‐contact; Brochure 4. No pre‐contact; No brochure | |
| Outcomes | Response within 67 days | |
| Topic | Non‐health: Business, Employment, and Finance | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Alutto 1970.
| Methods | Random allocation: alternation | |
| Data | Members of a western New York State chamber of commerce | |
| Comparisons | 1. Questionnaire sent to work address 2. Questionnaire sent to home address | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes towards universities | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Andreasen 1970.
| Methods | Random allocation: method not specified | |
| Data | New York State lottery winners | |
| Comparisons | 1. Mimeographed salutation; Follow‐up mimeographed
2. Mimeographed salutation; Follow‐up handwritten
3. Hand‐typed salutation;
Follow‐up mimeographed
4. Hand‐typed salutation; Follow‐up handwritten
5. Hand‐typed salutation using name of participant with hand‐written postscript; Follow‐up mimeographed
6. Hand‐typed salutation using name of participant with hand‐written postscript; Follow‐up handwritten Follow‐up letters sent after 3 weeks. Follow‐up questionnaires sent after 4 weeks. |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Arzheimer 1999.
| Methods | Random allocation: method not specified | |
| Data | A random sample of people listed on registration file, Hamburg, Germany | |
| Comparisons | 1. Phonecard worth 6 Deutsch marks included 2. No incentive | |
| Outcomes | Response in first wave of mailing | |
| Topic | Non‐health: Voting behaviour | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Asch 1996.
| Methods | Random allocation: method not specified | |
| Data | Subscribers to Nursing who had previously indicated practice in critical care settings (US) | |
| Comparisons | 1. Questionnaire sent 3 times 2. Questionnaire sent with postcard. If postcard was returned, participant received no follow‐up mailings | |
| Outcomes | Response period not specified | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | Author contacted: no further information on allocation concealment | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Asch 1998.
| Methods | Random allocation: method not specified | |
| Data | Primary care physicians identified through the American Medical Association Physician Master File (US) | |
| Comparisons | 1. $2 incentive sent with questionnaire 2. $5 incentive sent with questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | Author contacted: no further information on allocation concealment | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ashing‐Giwa 2000.
| Methods | Random allocation: method not specified | |
| Data | A sample of African‐American and white American breast cancer patients diagnosed in 1989 and 1990 | |
| Comparisons | 1. $5 gift certificate sent with questionnaire 2. Promise of $5 gift certificate on response | |
| Outcomes | Response period not specified | |
| Topic | Health: Quality of life in long‐term breast cancer survivors | |
| Mode of Administration | Postal | |
| Notes | Mean age: 63.6 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Aveyard 2001.
| Methods | Random allocation: participants randomly sorted and then first 150 given intervention | |
| Data | 300 smokers selected randomly from 2 general practices in the United Kingdom | |
| Comparisons | 1. Pencil and eraser sent with questionnaire 2. No pencil or eraser sent with questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Health: Recruitment for a smoking cessation programme | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Bachman 1987.
| Methods | Random allocation: method not specified | |
| Data | Tax payers (Missouri) | |
| Comparisons | 1. Student sponsor; Social appeal 2. Student sponsor; Help the sponsor appeal 3. Business sponsor; Social appeal 4. Business sponsor; Help the sponsor appeal 5. Commercial sponsor; Social appeal 6. Commercial sponsor; Help the sponsor appeal | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Public attitude towards Missouri Department of Revenue | |
| Mode of Administration | Postal | |
| Notes | Author contacted: no further information on allocation concealment | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Barker 1996.
| Methods | Random allocation: using random number generation | |
| Data | Individuals randomly selected from electoral registers (Solihull, UK) | |
| Comparisons | 1. Question on sexual health included
2. Question on sexual health not included Reminder letter and questionnaire sent to non‐responders 3 weeks after initial mailing |
|
| Outcomes | Response period not specified | |
| Topic | Health: Sexual health | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Bauer 2004.
| Methods | Random allocation | |
| Data | People who participated both in the Community Intervention Trial for Smoking Cessation (COMMIT) as well as the follow‐up study | |
| Comparisons | 1. US$ 2 Cheque 2. US$ 10 Cheque 3. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Smoking cessation | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly 48‐57 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Becker 2000a.
| Methods | Random allocation: method not specified | |
| Data | BSN alumni who graduated between 1989 and 1997 who had not returned an initial survey | |
| Comparisons | 1. Second questionnaire sent as follow up 2. Postcard follow up (no second questionnaire) | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Professional experience since graduation and perceptions of academic preparation | |
| Mode of Administration | Postal | |
| Notes | Additional data obtained from author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Becker 2000b.
| Methods | Random allocation: method not specified | |
| Data | Alumni who graduated with a PhD or MSN between 1988 and 1997 who had not returned an initial survey | |
| Comparisons | 1. Second questionnaire sent as follow up 2. Postcard follow up (no second questionnaire) | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Professional experience since graduation and perceptions of academic preparation | |
| Mode of Administration | Postal | |
| Notes | Additional data obtained from author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Beebe 2005a.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Medicaid enrollees.Simple random sample | |
| Comparisons | 1. US$ 2 Bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Racial and ethnic disparities in the use of health services and barriers to care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Beebe 2005b.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Medicaid enrollees. American Indian | |
| Comparisons | 1. US$ 2 Bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Racial and ethnic disparities in the use of health services and barriers to care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Beebe 2005c.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Medicaid enrollees | |
| Comparisons | 1. US$ 2 Bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Racial and ethnic disparities in the use of health services and barriers to care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Beebe 2005d.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Medicaid enrollees. Somali | |
| Comparisons | 1. US$ 2 Bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Racial and ethnic disparities in the use of health services and barriers to care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Beebe 2005e.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Medicaid enrollees. Latino | |
| Comparisons | 1. US$ 2 Bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Racial and ethnic disparities in the use of health services and barriers to care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Beebe 2005f.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Medicaid enrollees. African American | |
| Comparisons | 1. US$ 2 Bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Racial and ethnic disparities in the use of health services and barriers to care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Beebe 2007.
| Methods | Random allocation: using RANUNI function in SAS | |
| Data | Mayo clinic patients | |
| Comparisons | 1. Small booklet (6 1/8 X 8 1/4") 2. Large booklet (8 1/4 X 11") 3. Blue booklet 8. White booklet |
|
| Outcomes | Response period not specified | |
| Topic | Health: Measure awareness and knowledge of privacy practices, and general opinions on privacy and health care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author; Mean age: 57.6 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Bell 2004.
| Methods | Random allocation : computerised random number generation | |
| Data | People who had signed up for the 'Adventist Health Study‐2' | |
| Comparisons | 1. Follow‐up phone call 2. No follow‐up phone call |
|
| Outcomes | Response within approximately 6 months | |
| Topic | Health: Dietary habits and risk of cancer | |
| Mode of Administration | Postal | |
| Notes | Me an age: 67.5 years; Additional data obtained from author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Bellizzi 1986.
| Methods | Random allocation: random draw | |
| Data | People randomly selected from a local city telephone directory, USA | |
| Comparisons | 1. $1 bill included with questionnaire 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Supermarket shopping | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Berdie 1973.
| Methods | Random allocation: method not specified | |
| Data | Staff of University of Minnesota, including professors of each rank | |
| Comparisons | 1. 1‐page questionnaire 2. 2‐ page questionnaire 3. 4‐ page questionnaire | |
| Outcomes | Response within 20 days | |
| Topic | Non‐health: Current social problems | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Bergen 1957.
| Methods | Random allocation: method not specified | |
| Data | Teachers in municipal elementary schools (Amsterdam) | |
| Comparisons | 1. Pre‐notification 2. None | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Berk 1993.
| Methods | Random allocation: method not specified | |
| Data | Physicians | |
| Comparisons | 1. $10 with first mailing; Follow‐up questionnaire and letter mentioning the incentive
2. No incentive with first mailing; Follow‐up questionnaire with a $10 incentive and letter explaining the importance of the study
3. No mention of $10 incentive in either first or second mailing Follow‐ups sent after 3 weeks |
|
| Outcomes | Response period not specified | |
| Topic | Health: Cost‐effectiveness of 2 alternative methods of diagnosing allergies | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Berry 1987.
| Methods | Random allocation: method not specified | |
| Data | Physician members of the American Medical Association | |
| Comparisons | 1. Cheque sent with first mailing
2. Promise of cheque with first mailing Non‐responders received a second mailing followed by a telephone call. If they no longer had the questionnaire, a third copy was sent |
|
| Outcomes | Response period not specified | |
| Topic | Health: Evaluation of National Institute of Health Consensus Development Programme | |
| Mode of Administration | Postal | |
| Notes | Mean age: 48 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Beydoun 2006.
| Methods | Random allocation: using computerised database | |
| Data | Women of reproductive age residing in Iowa county | |
| Comparisons | 1. Unconditional $5 Telephone card + Conditional $25 Check 2. Conditional $ 30 Check |
|
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Electronic: CATI | |
| Notes | Age: 18‐49 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Bhandari 2003.
| Methods | Random allocation: computerised random number generation | |
| Data | Surgeon members of the orthopaedic trauma association | |
| Comparisons | 1. Survey endorsed in cover letter by 'opinion leaders' (high profile surgeons) 2. Survey not endorsed | |
| Outcomes | Response period not specified | |
| Topic | Health: Evaluate surgeons opinions regarding optimal treatment of fractures of the tibial shaft | |
| Mode of Administration | Postal | |
| Notes | Mean age: 30.5 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Biner 1988.
| Methods | Random allocation: method not specified | |
| Data | Residents of a mid‐western US city | |
| Comparisons | 1. Reactance appeal; $1 incentive 2. Reactance appeal; No incentive 3. No reactance appeal; $1 incentive 4. No reactance appeal; No incentive | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Residents attitudes about the city | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Biner 1990.
| Methods | Random allocation: method not specified | |
| Data | Residents of a mid‐western US city | |
| Comparisons | 1. $1 incentive; Obligatory cover letter 2. $1 incentive; Appreciative cover letter 3. $0.25 incentive; Obligatory cover letter 4. $0.25 incentive; Appreciative cover letter | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Residents attitudes about the city | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Biner 1994.
| Methods | Random allocation: method not specified | |
| Data | Residents of a mid‐western US city | |
| Comparisons | 1. Short questionnaire; $1 incentive and obligatory cover letter 2. Short questionnaire; $1 incentive and appreciative cover letter 3. Long questionnaire; $1 incentive and obligatory cover letter 4. Long questionnaire; $1 incentive and appreciative cover letter | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Residents attitudes about the city | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Birnholtz 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | Users of a collaboratory for earthquake engineering research | |
| Comparisons | 1. $5 bill 2. Gift certificate for Amazon.com |
|
| Outcomes | Response period was 6 weeks | |
| Topic | Non‐health: Participants research work and perception of a set of collaboration tools | |
| Mode of Administration | Electronic: Web based | |
| Notes | Additional data obtained from the author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Blass 1981.
| Methods | Random allocation: method not specified | |
| Data | Certified psychologists who did not respond to previous mailing of the questionnaire | |
| Comparisons | 1. Consensus statement; Threat of follow up 2. Consensus statement; No threat of follow up 3. No consensus statement; Threat of follow up 4. No consensus statement; No threat of follow up | |
| Outcomes | Response period not specified | |
| Topic | Health: Psychologist behavior and attitudes towards continuing education | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Blass‐Wilhems 1982.
| Methods | Random allocation: random walk sampling | |
| Data | Not known | |
| Comparisons | 1. Real postage stamp 2. Postage paid reply | |
| Outcomes | — | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Blomberg 1996.
| Methods | Random allocation: using a list of numbers between 1‐99 selected in a 'random' order by a researcher | |
| Data | Patients at the Stockholm County Council Institute of Psychotherapy | |
| Comparisons | 1. Questionnaire with promise of lottery ticket on response
2. Questionnaire with lottery ticket enclosed
3. Questionnaire with no incentive All non‐respondents were sent reminders at 3, 6 and 10 weeks after initial mailing At 14 weeks, non‐responders were sent a brief questionnaire regarding their reasons for not responding |
|
| Outcomes | Response within 12 weeks. Response period for second questionnaire not specified | |
| Topic | Health: Psychotherapy measures ‐ General Symptom Index, Sense of Coherence, and Change in Target Complaints | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Author confirmed allocation concealment | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Blythe 1986.
| Methods | Random allocation: method not specified | |
| Data | Social workers | |
| Comparisons | 1. Questionnaire with an opportunity to enter a lottery
2. Questionnaire without lottery offer Reminder letter sent after 1 week. Non‐ respondents followed‐up at 3 and 7 weeks with offer to participate in the lottery. |
|
| Outcomes | Response within 30 days | |
| Topic | Health: Application of clinical evaluation tools in practice | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Boser 1990.
| Methods | Random allocation: alternation | |
| Data | Graduates from the College of Education of a major university (US) | |
| Comparisons | 1. Questionnaire in folder format 2. Questionnaire in stapled format | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Teaching | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Bosnjak 2003.
| Methods | Random allocation: computerised random number generation | |
| Data | Local professional sales association members in the mid‐atlantic US | |
| Comparisons | 1. Unconditional $2 via Paypal 2. Conditional $2 3. Conditional Prize draw (two $50 and four $25 prizes) 4. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Non‐Health: Trends and concerns in real estates | |
| Mode of Administration | Electronic: Web survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate. |
Bredart 2002.
| Methods | Random allocation: method not specified | |
| Data | Breast cancer patients undergoing surgical treatment within the surgery department of the European Institute of Oncology in Milan | |
| Comparisons | 1. Questionnaire sent 2 weeks after hospital discharge 2. Questionnaire sent 3 months after hospital discharge | |
| Outcomes | Response period not specified | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brehaut 2006.
| Methods | Random allocation: computerised random number generation | |
| Data | Members of the Canadian Association of Emergency Physicians | |
| Comparisons | 1. Single sided print format 2. Double sided print format 3. Known sender recognition 4. Unknown sender recognition |
|
| Outcomes | Response period not specified | |
| Topic | Health: Clinical decision rules | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Brems 2006.
| Methods | Random allocation: alternation | |
| Data | Licensed healthcare professionals from Alaska and New Mexico in the US | |
| Comparisons | 1. First‐class mail 2. Priority mail |
|
| Outcomes | Response period not specified | |
| Topic | Health: Range of treatment used by physical and behavioural healthcare providers, ethical issues | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Brennan 1991.
| Methods | Random allocation: method not specified | |
| Data | People listed on 1 of the 57 electoral rolls representing the main urban centres, New Zealand | |
| Comparisons | 1. Control ‐ no incentive 2. 20c coin with first mailing 3. 50c coin with first mailing 4. $1 note with first mailing 5. 20c coin with second mailing 6. 50c coin with second mailing 7. $1 note with second mailing 8. Entry into prize draw for $200 cash offered with each mail out 9. Entry into prize draw for $200 gift voucher offered with each mail out | |
| Outcomes | Response within 21 days of the third mailing (49 days after initial mailing) | |
| Topic | Non‐health: Personal finance status | |
| Mode of Administration | Postal | |
| Notes | Randomisation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brennan 1992a.
| Methods | Random allocation: method not specified | |
| Data | People listed on a financial service company's 'hot prospect' list | |
| Comparisons | 1. $0.50 incentive 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Finances and shopping behaviours | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brennan 1992b.
| Methods | Random allocation: method not specified | |
| Data | People listed on the electoral roll (New Zealand) | |
| Comparisons | 1. $0.50 incentive 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Finances and shopping behaviours | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brennan 1992c.
| Methods | Random allocation: method not specified | |
| Data | People listed on the electoral roll (New Zealand) | |
| Comparisons | 1. $0.50 incentive 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Finances and shopping behaviours | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brennan 1993a.
| Methods | Random allocation: method not specified | |
| Data | Dairy and beef farmers | |
| Comparisons | 1. $0.50 coin with first mailing 2. $1 coin with first mailing 3. $1 lottery ticket with first mailing 4. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brennan 1993b.
| Methods | Random allocation: method not specified | |
| Data | People listed on the electoral roll (New Zealand) | |
| Comparisons | 1. $0.50 coin with first mailing 2. $1 coin with first mailing 3. Promise that $1 would be donated to a charity for each valid return (in each of 3 mailings) 4. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Bright 2002.
| Methods | Random allocation: method not specified | |
| Data | US Marinas | |
| Comparisons | 1. Offer of entry into a prize draw and summary of study results on return of questionnaire 2. No incentive offered | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perceptions of decision makers at US Marinas | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brook 1978.
| Methods | Random allocation: alternation. | |
| Data | People who had been interviewed when shopping (Southampton, UK) | |
| Comparisons | 1. First class stamp out; First class stamp return 2. First class stamp out; Second class stamp return 3. Second class stamp out; First class stamp return 4. Second class stamp out; Second class stamp return 5. First class stamp out; Second class business reply return 6. Second class stamp out; Second class business reply return | |
| Outcomes | Response within 2 weeks | |
| Topic | Non‐health: Marketing | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Brown 1965.
| Methods | Random allocation: method not specified | |
| Data | Non‐paediatric physicians (US) | |
| Comparisons | 1. 2‐ page questionnaire (first page was letter with 2 cystic fibrosis screening questions; second page asked for details of patients seen) 2. 1‐page cover letter and postcard with 2 cystic fibrosis screening questions | |
| Outcomes | Response period not specified | |
| Topic | Health: Cystic fibrosis | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brown 1975.
| Methods | Random allocation: method not specified | |
| Data | Officers and enlisted men | |
| Comparisons | 1. Pre‐notification; Randomised enquiry method 2. No pre‐notification; Randomised enquiry method 3. Pre‐notification; Conventional method 4. No pre‐notification; Conventional method | |
| Outcomes | Response period not specified | |
| Topic | Health: Assessment of illicit drug use | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Bruce 2000.
| Methods | Random allocation: method not specified | |
| Data | People randomly selected from households in central Sydney (Australia) who had agreed to participate during an earlier phone interview | |
| Comparisons | 1. Phone call reminder to non‐responders 2. Postcard reminder to non‐responders | |
| Outcomes | Response period not specified | |
| Topic | Health: Colorectal Cancer Screening | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Brøgger 2007.
| Methods | Random allocation: method not specified | |
| Data | Permanent residents of Norway | |
| Comparisons | 1. Postal plus optional Internet response 2. Only postal response |
|
| Outcomes | Response period not specified | |
| Topic | Health: Respiratory survey (to establish the occurrence and risk factors for asthma and allergies) | |
| Mode of Administration | Postal | |
| Notes | Mean age: 30.7 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Buchman 1982.
| Methods | Random allocation: alternation | |
| Data | Certified public accountants | |
| Comparisons | 1. Conventional questionnaire 2. Randomised response technique employed for each question | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Audit procedures | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Burns 1980.
| Methods | Random allocation: method not specified | |
| Data | A random sample of bank and savings and loan chief executive officers, USA | |
| Comparisons | 1. No incentive; No follow up 2. 25 cent incentive; No follow up 3. 25 cent incentive; Follow‐up postcard sent 10 days after initial mailing 4. No incentive; Follow‐up postcard sent 10 days after initial mailing | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Commercial population | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Buttle 1997.
| Methods | Random allocation | |
| Data | Managing Directors of the companies listed on the DTI Quality Assurance Register 1995 | |
| Comparisons | 1. Questionnaires printed on white paper 2. Questionnaires printed on yellow paper |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perceived costs and benefits of ISO 9000 in certified organisations | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Cabana 2000.
| Methods | Random allocation: method not specified | |
| Data | Paediatricians listed as general paediatricians in the American Medical Association master file | |
| Comparisons | 1. Survey logo on questionnaire only 2. Survey logo on cover letter, return envelope, questionnaire and outer envelope | |
| Outcomes | Response period not specified | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Campbell 1990.
| Methods | Random allocation: method not specified | |
| Data | People listed on the electoral roll (Southampton, UK) | |
| Comparisons | 1. Participants told replies would be anonymous 2. Participants told replies would not be anonymous and would be followed‐up after 3 weeks | |
| Outcomes | Response period not specified | |
| Topic | Health: Knowledge of AIDS | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Camunas 1990.
| Methods | Random allocation: method not specified | |
| Data | Nurses who were members of the New York State Nurses Association | |
| Comparisons | Experiment 1:
1. Questionnaire, cover letter and brochure
2. Questionnaire, cover letter with an invitation to join the Nursing association and brochure
3. Questionnaire and cover letter only Experiment 2: 1. Questionnaire, cover letter and $1bill incentive 2. Questionnaire and cover letter only Questionnaires were colour‐coded for each group. No pre‐contact or follow up used |
|
| Outcomes | Response period not specified | |
| Topic | Health: Professional membership behaviour | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Carling 2004.
| Methods | Random allocation:method not specified | |
| Data | Journalists in the health field | |
| Comparisons | 1. International postal vouchers 2. No International postal vouchers |
|
| Outcomes | Response period not specified | |
| Topic | Health: barriers and facilitators to high quality health journalism | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Carpenter 1974.
| Methods | Random allocation: method not specified | |
| Data | People listed on an automobile registration list (Arizona, US) | |
| Comparisons | 1. Least personalised questionnaire 2. Somewhat personalised questionnaire 3. Most personalised questionnaire 4. Control group | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Migration behaviour | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Carpenter 1977.
| Methods | Random allocation: alternation | |
| Data | Heads of households and their spouses selected from the annually compiled auto registration list | |
| Comparisons | 1. 2 questionnaires allocated per household 2. 1 questionnaire allocated per household | |
| Outcomes | Response within 7 weeks | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Cartwright 1986.
| Methods | Random allocation: method not specified | |
| Data | Recent mothers | |
| Comparisons | Experiment 1:
1. Long questionnaire about facts and attitudes
2. Medium questionnaire about facts and attitudes
3. Short questionnaire about facts and attitudes
4. Long questionnaire about facts only
5. Medium questionnaire about facts only
6. Short questionnaire about facts only Experiment 2: 1. Government department sponsor (OPCS, UK) 2. University sponsor (Institute for Social Studies in Medical Care) Experiment 3: 1. Asked to tick boxes in response 2. Asked to ring pre‐codes in response |
|
| Outcomes | — | |
| Topic | Health: Maternity | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Cartwright 1987.
| Methods | Random allocation: systematic division | |
| Data | Elderly people from the electoral registers in Woodford and Wanstead, London and Blackley, Manchester, UK | |
| Comparisons | 1. Shorter questionnaire (2 questions) 2. Longer questionnaire (5 questions) | |
| Outcomes | — | |
| Topic | Health: Medication and relationship with GPs | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Chan 2003.
| Methods | Random allocation: computerised random number generation | |
| Data | Chinese Medicine Practitioners registered with the Chinese Medicine Council of Hong Kong | |
| Comparisons | 1. HK $ 20 2. HK $ 30 3. No Incentives |
|
| Outcomes | Response period not specified | |
| Topic | Health: Knowledge, attitudes, and practices on computers and computer use in clinical practice | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly 40‐59 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Chebat 1991.
| Methods | Random allocation: method not specified | |
| Data | The Quebec population within the legal driving age | |
| Comparisons | 1. Pre‐notification; Non‐monetary incentive 2. Pre‐notification; No incentive 3. No pre notification; Non‐monetary incentive 4. No pre notification; No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Driving behaviour | |
| Mode of Administration | Postal | |
| Notes | Method of allocation and concealment ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Chen 1984.
| Methods | Random allocation: method not specified | |
| Data | Students from 4 Taipei Universities | |
| Comparisons | 1.Long questionnaire ‐ 5 pages 2. Short questionnaire ‐ 2 pages 3. High salient topic ‐ cutting‐class behaviours in undergraduates 4. Low salient topic ‐ cutting‐class behaviours in PhD students 5. High authority researcher ‐ University professor with a PhD in Psychology 6. Low authority researcher ‐ Student from the Psychology department. |
|
| Outcomes | Response period within 10 days | |
| Topic | Non‐health: Class cutting behaviour | |
| Mode of Administration | Postal | |
| Notes | Language of publication is Chinese | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Childers 1979.
| Methods | Random allocation: method not specified | |
| Data | Agents of large Midwest‐based multiple‐line insurance company (US) | |
| Comparisons | 1. Advance letter with commitment postcard. Asked to return the postcard to say if will participate and how long they will take to respond. 'Yes' responses then sent a questionnaire
2. Advance letter with commitment postcard. Asked to return the postcard only to say if will participate. 'Yes' responses then sent questionnaire
3. Control ‐ no prior commitment sought. All sent questionnaires Reminder postcards sent after 4 days. Non respondents sent another questionnaire after 3 weeks |
|
| Outcomes | — | |
| Topic | Non‐health: Insurance | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Childers 1980a.
| Methods | Random allocation: method not specified | |
| Data | Academics on the American Marketing Association Roster | |
| Comparisons | 1. Egoistic appeal; Hand‐written postscript
2. Egoistic appeal; Typed postscript
3. Help the sponsor appeal; Hand‐written postscript
4. Help the sponsor appeal; Typed postscript
5. Social utility appeal; Hand‐written postscript
6. Social utility appeal; Typed postscript All participants received reminders after 1 week |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing texts | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Childers 1980b.
| Methods | Random allocation: method not specified | |
| Data | Business practitioners on a mailing list of a major south‐western university (US) | |
| Comparisons | 1. Egoistic appeal; Hand‐written postscript
2. Egoistic appeal; Typed postscript
3. Help the sponsor appeal; Hand‐written postscript
4. Help the sponsor appeal; Typed postscript
5. Social utility appeal; Hand‐written postscript
6. Social utility appeal; Typed postscript All participants received reminders after 1 week |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing texts | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Childers 1985.
| Methods | Random allocation: method not specified | |
| Data | Policyholders of a national insurance company (US) | |
| Comparisons | 1. Computer‐printed out‐going envelope, computer‐printed return‐envelope, cover letter explained name and address were for research only 2. Computer‐printed out‐going envelope, computer‐printed return‐envelope, cover letter did not explain name and address were for research only 3. Computer‐printed out‐going envelope, participants given provision to write own name and address on return envelope, cover letter explained name and address were for research only 4. Computer‐printed out‐going envelope, participants given provision to write own name and address on return envelope, cover letter did not explain name and address were for research only 5. Labelled address on out‐going envelope, computer‐printed return address, cover letter explained name and address were for research only 6. Labelled address on out‐going envelope, computer‐printed return address, cover letter did not explain name and address were for research only 7. Labelled address on out‐going envelope, participants given provision to write own name and address on return envelope, cover letter explained name and address were for research only 8. Labelled address on out‐going envelope, participants given provision to write own name and address on return envelope, cover letter did not explain name and address were for research only | |
| Outcomes | Response within 12 days | |
| Topic | Non‐health: Payment of car insurance | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Childers TL 1979.
| Methods | Random allocation: alternation | |
| Data | American marketing association practitioner members | |
| Comparisons | 1. Small paper size (8½ X 11") 2. Large paper size (8½ X 14") 3. Single sided 4. Double sided |
|
| Outcomes | — | |
| Topic | Non‐health: Marketing concepts, Employment features | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate. |
Choi 1990.
| Methods | Random allocation: computerised random number generation | |
| Data | Members of the Ontario Nurses' Association | |
| Comparisons | 1. No stamp on return envelope 2. Business‐reply stamp 3. Metered stamp 4. Small regular stamp 5. Large commemorative stamp | |
| Outcomes | Response within 92 days | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Christie 1985.
| Methods | Random allocation: alternation | |
| Data | People aged 18+ years listed in the 1984 Auckland telephone directory, New Zealand | |
| Comparisons | 1. Hand written signature on covering letter (HW); Actual age and income asked for (AAI); Typed address on outgoing envelope (Ty) 2. HW; AAI; Hand written address on outgoing envelope (HE) 3. HW; Age and income bracket asked for (AIB); Ty 4. HW; AIB; HE 5. Typed signature on covering letter (T); AAI; Ty 6. T; AAI; HE 7. T; AIB; Ty 8. T; AIB; HE | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing ‐ awareness of macadamia nuts, purchase behaviour | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Church 2004.
| Methods | Random allocation: method not specified | |
| Data | Residents of Wright County in Minnesota, US | |
| Comparisons | 1. Only questionnaire 2. Questionnaire + Faecal Occult Blood Test (FOBT) ‐ No reminder 3. Questionnaire + Faecal Occult Blood Test (FOBT) + Reminder |
|
| Outcomes | Response period not specified | |
| Topic | Health: Colorectal screening | |
| Mode of Administration | Postal | |
| Notes | Mean age: 63 years; Mainly females; 49 % of participants belonging to group 2 was inadvertently delivered the 1st reminder | |
Clark 2001.
| Methods | Random allocation: computerised random number generation | |
| Data | All consultants listed on the Royal College of Obstetricians and Gynaecologists database (UK) | |
| Comparisons | 1. Simple plastic ballpoint pen sent with questionnaire. 2. No pen | |
| Outcomes | Response period not specified | |
| Topic | Health: Views on gynaecological endoscopy | |
| Mode of Administration | Postal | |
| Notes | 1 reminder was sent to all non‐responders 3 months after initial mailing | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Clark TJ 2001.
| Methods | Random allocation: computerised random number generation | |
| Data | All gynaecologists identified from the British Society of Gynaecological Endoscopy database of members | |
| Comparisons | 1. Questionnaire and covering letter printed on standard quality white paper 2. Questionnaire and covering letter printed on high quality white paper | |
| Outcomes | Response period not specified | |
| Topic | Health: Hysteroscopy | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Clarke 1998.
| Methods | Random allocation: computerised random number generation | |
| Data | Study survivors resident in 3 health authority areas | |
| Comparisons | 1. 3 extra questions on current sources of income included 2. Extra questions not included 3. Extra questionnaire on cognitive functioning included 4. Extra questionnaire not included | |
| Outcomes | Response period not specified | |
| Topic | Health: Whitehall study | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Mean age: 77 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Clausen 1947.
| Methods | Random allocation: systematic division | |
| Data | Non‐respondents to an earlier survey | |
| Comparisons | 1. Impersonal salutation; Handwritten signature; Franked outward envelope 2. Impersonal salutation; Facsimile signature; Franked outward envelope 3. Personal salutation; Facsimile signature; Franked outward envelope 4. Personal salutation; Handwritten signature; Franked outward envelope 5. Personal salutation; Handwritten signature; Air mail and special delivery outward envelope | |
| Outcomes | Response within 4 weeks | |
| Topic | Health: National Service Life Insurance (NSLI) | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Claycomb 2000.
| Methods | Random allocation: method not specified | |
| Data | Marketing executives and managers representing a geographic cross section of the US | |
| Comparisons | Intervals between the original and 2 rounds of follow‐up mailings: 1. 3 days 2. 6 days 3. 9 days 4. 12 days 5. 15 days 6. 18 days 7. 21 days 8. 24 days 9. 27 days 10. 30 days 11. 33 days 12. 36 days 13. 39 days 14. 42 days 15. 45 days 16. 48 days 17. 51 days 18. 54 days 19. 57 days 20. 60 days | |
| Outcomes | Response after 3 mailings | |
| Topic | Non‐health: Companies customer relation practices | |
| Mode of Administration | Postal | |
| Notes | Dates of initial mailings randomised to prevent seasonal biases | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Cleopas 2006.
| Methods | Random allocation: computerised random number generation | |
| Data | Adults discharged from teaching hospital system in Geneva | |
| Comparisons | 1. 2‐original response format (yes/no) 2. 3‐point similarity format (applies completely/in part/not at all) 3. 5‐point intensity format (completely true to completely false) 4. 5‐point frequency format (all the time to never). |
|
| Outcomes | Response period not specified | |
| Topic | Health: Patient based outcome measure (Nottingham Health Profile) | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate. |
Cobanoglu 2003.
| Methods | Random allocation: computerised random number generation | |
| Data | Managers who are members of the American Management Association (AMA) | |
| Comparisons | 1. Luggage tag (LT) 2. Prize draw for a personal digital assistant (PDA) 3. Prize draw for both LT + PDA 4. Control. |
|
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | Adequate |
Cockayne 2005.
| Methods | Random allocation | |
| Data | Community dwelling women aged over 70 years living in the York and Cumbria area | |
| Comparisons | 1. Offer of study results 2. Control |
|
| Outcomes | Response period not specified | |
| Topic | Health: Calcium and Vitamin D supplementation for fracture prevention | |
| Mode of Administration | Postal | |
| Notes | Independent researchers from the York Trials Unit randomised the eligible women. Administration of the questionnaire was not blind to group allocation Age: Above 70 years; Mainly females |
|
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | Adequate. |
Collins 2000.
| Methods | Random allocation: method not specified | |
| Data | Members of the RAND adolescent / young adult panel study drawn from schools across the US | |
| Comparisons | 1. $20 cash with mailing 2. $20 cash promised on return of questionnaire 3. $25 cash promised on return of questionnaire | |
| Outcomes | Response within approximately 4 months | |
| Topic | Health: Substance use, problem behavior, predictors of risk behavior, attitudes and beliefs | |
| Mode of Administration | Postal | |
| Notes | Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Corcoran 1985.
| Methods | Random allocation: method not specified | |
| Data | Masters level social workers | |
| Comparisons | 1. First class stamped return envelope
2. Reply permit return envelope Follow‐up postcard sent to all subjects 3 to 4 weeks after original mailing |
|
| Outcomes | Response period not specified | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Cox 1974.
| Methods | Random allocation: method not specified | |
| Data | Residents of a south‐western city listed in the metropolitan telephone directory (US) | |
| Comparisons | 1. Personalised cover letter; Follow‐up postcard after 3 days 2. Personalised cover letter; No follow‐up postcard 3. No personalised cover letter; Follow‐up postcard after 3 days 4. No personalised cover letter; No follow‐up postcard | |
| Outcomes | Response within 16 days | |
| Topic | Non‐health: Finance ‐ appraise consumer evaluations of financial institutions | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Crittenden 1985.
| Methods | Random allocation: method not specified | |
| Data | Alumni members of a National Business School | |
| Comparisons | 1. White questionnaire 2. Yellow questionnaire 3. Questionnaire using Letter quality printer 4. Questionnaire using Dot‐matrix printer |
|
| Outcomes | Response period not specified | |
| Topic | Non health: Education | |
| Mode of Administration | Postal | |
| Notes | 2 x 2 Factorial design | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Cycyota 2002.
| Methods | Random allocation: method not specified | |
| Data | Businesses form the state sales and use of license records in the Southwestern region of US | |
| Comparisons | 1. US $1 bill 2. No incentive 3. Advance notice 4. No advance notice 5. Personalised salutation 6. No personalised salutation 7. Telephone follow up 8. No telephone follow up |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Employment | |
| Mode of Administration | Postal | |
| Notes | 2 X 2 X 2 X 2 X 2 fully crossed factorial design; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Deehan 1997.
| Methods | Random allocation: method not specified | |
| Data | GPs who did not respond to 2 mailings of a questionnaire (UK) | |
| Comparisons | Third mailing:
1. No incentive
2. £5 charity donation
3. £10 charity donation
4. £5 payment
5. £10 payment Fourth mailing to non responders in control group of third mailing: 1. £5 payment 2. £10 payment |
|
| Outcomes | Response period not specified | |
| Topic | Health: Information on clinical work with alcohol misusing patients | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Del Valle 1997.
| Methods | Random allocation: method not specified | |
| Data | Members of the American Association of Neurologists who did not respond to 2 earlier mailings | |
| Comparisons | 1. Questionnaire sent by certified mail with return receipt request postcard 2. Questionnaire sent by first class mail | |
| Outcomes | Response period not specified | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Delnevo 2004.
| Methods | Random allocation: using a statistical software package | |
| Data | New Jersey Internists, general practitioners, family physicians, paediatricians, and obstetrician and gynaecologists | |
| Comparisons | 1. Up‐front $25 gift card 2. Promised $25 gift card |
|
| Outcomes | Response period not specified | |
| Topic | Health: Smoking cessation ‐ attitudes and practice | |
| Mode of Administration | Postal | |
| Notes | The investigators were not blinded to the treatment allocation ‐ confirmed by the author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Denton 1988.
| Methods | Random allocation: method not specified | |
| Data | Graduates from the Department of Educational Curriculum and Instruction at a large university in the south‐west (US) | |
| Comparisons | 1. No incentive 2. Newsletter 3. $0.25 4. $0.25 and newsletter | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Education | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Denton 1991.
| Methods | Random allocation: method not specified | |
| Data | Experiments 1 and 2: Graduates from the Department of Educational Curriculum and Instruction at a large university in the south‐west (US) | |
| Comparisons | Experiment 1:
1. No incentive
2. Newsletter
3. $0.25
4. $0.25 and newsletter Experiment 2: 1. No incentive 2. $0.25 3. $0.50 4. $1 5. Raffle |
|
| Outcomes | Experiment 2 : Response within 2 months | |
| Topic | Non‐health : Classroom teachers pedagogical knowledge and skills | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Deutskens 2004a.
| Methods | Random allocation: using random number generation in SPSS | |
| Data | Participants of the multi‐client attitude and usage study in the Netherlands | |
| Comparisons | 1. 2 Euros voucher for an online book and CD store 2. 5 Euros voucher for an online book and CD store 3. Lotteries to win vouchers worth 25 Euros 4. Lotteries to win vouchers worth 50 Euros 5. Charity donation of 500 Euros to either World Wide Fund for Nature (WWF), Amnesty International, or a Cancer Association 6. Short version of the questionnaire 7. Long version of the questionnaire 8. Visual presentation of response categories 9. Textual presentation of response categories 10. Early follow up (after 1 week) 11. Late follow up (after 2 weeks) |
|
| Outcomes | Response period not specified | |
| Topic | Non health: Marketing | |
| Mode of Administration | Electronic: Online survey | |
| Notes | 3 X 2 X 2 X 2 Factorial design. Method of allocation ascertained through contact with author. Age: Mostly 35‐49; Mainly males |
|
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Deutskens 2004b.
| Methods | Random allocation: using random number generation in SPSS | |
| Data | University students | |
| Comparisons | 1. Lottery to win 1 out of 10 vouchers of 25 Euros 2. Lottery to win 1 out of 5 vouchers of 50 Euros 3. Lottery to win a DVD Player |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Education | |
| Mode of Administration | Electronic: Online | |
| Notes | Method of allocation ascertained through contact with author; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | Adequate |
Dillman 1974a.
| Methods | Random allocation: method not specified | |
| Data | A group of Washington State University alumni | |
| Comparisons | 1. Personalised cover letter 2. Non‐ personalised cover letter | |
| Outcomes | Response after 4 mailings | |
| Topic | Non‐health: Feelings and concerns about Washington State University | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained to be random through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dillman 1974b.
| Methods | Random allocation: method not specified | |
| Data | A systematic sample of people listed in the phone directories of Washington state, USA | |
| Comparisons | 1. No pre‐contact 2. Telephone pre‐contact | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Feelings and concerns about Washington State University | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained to be random through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dillman 1993.
| Methods | Random allocation: method not specified | |
| Data | Housing units identified by the census bureaus address control file | |
| Comparisons | 1. 1990 short form (control) questionnaire 2. Booklet 3. Micro form 4. Micro form requesting SSN 5. Roster form | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Census | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dillman 1996.
| Methods | Random allocation: method not specified | |
| Data | National probability sample of households in the USA | |
| Comparisons | 1. Control group 2. Benefit appeal on envelope and insert; Strong confidentiality assurance 3. Benefit appeal on envelope and insert; Standard confidentiality assurance 4. Mandatory appeal on envelope and insert; Strong confidentiality assurance 5. Mandatory appeal on envelope and insert; Standard confidentiality assurance 6. Mandatory appeal on envelope only; No confidentiality assurance | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Census | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | D ‐ Not used |
Dirmaier 2007.
| Methods | Random allocation: using computer assisted algorithm | |
| Data | Patients admitted for Psychotherapeutic treatment | |
| Comparisons | 1. Long questionnaire 2. Short questionnaire 3. 5 German Mark bill 4. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Mental Health outcome and treatment research | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly 40‐59; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dodd 1987.
| Methods | Random allocation: using a table of random numbers | |
| Data | Women employed full‐time in various civil servant positions at a university (US) | |
| Comparisons | 1. Hand‐signed, professor status, female author 2. Hand‐signed, student status, female author 3. Hand‐signed, professor status, male author 4. Hand‐signed, student status, male author 5. Photocopied signature, professor status, female author 6. Photocopied signature, student status, female author 7. Photocopied signature, professor status, male author 8. Photocopied signature, student status, male author | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Allocation concealment not described; Mean age: 42 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 1980a.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in the Cincinnati telephone directory (US) | |
| Comparisons | 1. Questionnaire with low threat follow up
2. Questionnaire with low‐moderate follow up
3. Questionnaire with low‐moderate follow up
(different to above)
4. Questionnaire with moderate follow up
5. Questionnaire with follow up
with moderate appeal
6. Questionnaire with prepaid incentive of 25 cents in follow up
7. Personally asked to compare the relative noxiousness of the threat of appeals sent to groups 1‐4 Non‐respondents to the initial mailings were followed‐up |
|
| Outcomes | Response within 31 days. | |
| Topic | Non‐health: Attitudes towards questionnaire, socio‐ demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 1980b.
| Methods | Random allocation: alternation | |
| Data | Individuals listed in the Cincinnati telephone directory (US) | |
| Comparisons | 1. Questionnaire with ID number typed on lower right‐hand corner of last page 2. As above, with words: 'Please do not remove identifying code number' typed to next to the ID number | |
| Outcomes | Response within 13 days | |
| Topic | Non‐health: Attitudes towards questionnaire, socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Dommeyer 1985.
| Methods | Random allocation: method not specified | |
| Data | Undergraduate business students (US) | |
| Comparisons | 1. Interesting questionnaire; No summary of results offered 2. Interesting questionnaire; Results summary offered 3. Uninteresting questionnaire; No summary of results offered 4. Uninteresting questionnaire; Results summary offered | |
| Outcomes | — | |
| Topic | Non‐health: Finance ‐ Tax survey; Mind Inventory Catalogue | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 1987.
| Methods | Random allocation using alternation | |
| Data | Telephone owners in Cincinnati | |
| Comparisons | 1. Negative appeal mention of follow up 2. Usual mail 3. Prepaid incentive of 25 cent each |
|
| Outcomes | Response to be received by 28th June | |
| Topic | Non‐health: Attitudes and familiarity towards mail; Education, Employment | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Dommeyer 1988.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in the Chicago and Phoenix telephone directory | |
| Comparisons | Different postscripts used on letter depending on intervention:
1. No incentive
2. 25 cent coin
3. 25 cent cheque
4. 25 cent money order
5. Early bird ‐ get a share in an incentive ($25) if send questionnaire back quickly
6. Sweep stake (entered into sweepstake to win $25 if return questionnaire by deadline) All participants sent cover letter and questionnaire in window envelope |
|
| Outcomes | — | |
| Topic | Non‐health: Product tampering and Morality Conscience Guilt Scale | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 1989.
| Methods | Random allocation: method not specified | |
| Data | Personal computer owners, manufacturers and retailers | |
| Comparisons | 1. Cover letter stressed importance of response and emphasised that respondents' names would never be placed on the questionnaire (control group) 2. Second paragraph offered respondents a summary of the results 3. Standard cover letter. Offer of a copy of the results made in a separate 'lift' letter | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Knowledge and attitudes towards computer counterfeiting | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 1991.
| Methods | Random allocation: method not specified | |
| Data | Californian residents who were entitled to a refund | |
| Comparisons | 1. Teaser printed on envelope 2. No teaser on envelope | |
| Outcomes | Response within 2 weeks | |
| Topic | Non‐health: Finance ‐ Awareness and attitudes towards insurance refunds | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 1996.
| Methods | Random allocation: method not specified | |
| Data | People listed in a telephone directory (Los Angeles, USA) | |
| Comparisons | 1. Photograph of an 'attractive' researcher printed on cover letter 2. No photo printed on cover letter | |
| Outcomes | — | |
| Topic | Non‐health: Attitudes towards music censorship and warning stickers on music albums | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dommeyer 2004.
| Methods | Random allocation: using randomised incomplete block design | |
| Data | Undergraduate business major students at California State University | |
| Comparisons | 1. Grade incentive 2. In‐class Demonstration of the web survey 3. Early grade feedback 4. Control |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Education | |
| Mode of Administration | Electronic: Online survey | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Donaldson 1999.
| Methods | Random allocation: method not specified | |
| Data | Physicians randomly selected from a list of US physicians actively caring for at least 1 transplant patient | |
| Comparisons | 1. $5 check with initial mailing; No follow‐up call 2. $5 check with initial mailing; Follow‐up call to non‐responders 4 weeks after initial mailing 3. No incentive; No follow‐up call 4. No incentive; Follow‐up call to non‐responders 4 weeks after initial mailing | |
| Outcomes | — | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | Mean age: 47 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Doob 1971a.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in a phone book (Toronto and Ontario, Canada) | |
| Comparisons | 1. No reactance (letter written normally); No incentive 2. No reactance; Dime incentive 3. Reactance (request written to make participants feel an attempt was being made to limit their freedom); No money 4. Reactance; Dime incentive | |
| Outcomes | Response within 2 weeks | |
| Topic | Health: Knowledge that smoking causes cancer | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Doob 1971b.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in a phone book (Toronto and Ontario, Canada) | |
| Comparisons | 1. No reactance (letter written normally); No incentive 2. No reactance; Dime incentive 3. Reactance (request written to make participants feel an attempt was being made to limit their freedom); No money 4. Reactance; Dime incentive | |
| Outcomes | Response within 2 weeks | |
| Topic | Health: Knowledge that smoking causes cancer | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Doob 1971c.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in a phone book (Toronto and Ontario, Canada) | |
| Comparisons | 1. No reactance (letter written normally); No incentive 2. No reactance; 20 cents incentive 3. Reactance (request written to make participants feel an attempt was being made to limit their freedom); No money 4. Reactance; 20 cents incentive | |
| Outcomes | Response within 2 weeks | |
| Topic | Health: Knowledge that smoking causes cancer | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Doob 1973.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in a telephone directory (Canada) | |
| Comparisons | 1. 20 cents incentive
2. 5 cents incentive
3. No incentive 1. University sponsor 2. Industrial sponsor |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Automobile ownership, duration spend on watching TV | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Doody 2003a.
| Methods | Random allocation: method not specified | |
| Data | US radiologist technologists who had not responded to 2 earlier mailings of a questionnaire | |
| Comparisons | 1. US first class mail; No incentive 2. US first class mail; $1 bill 3. US first class mail; $2 bill 4. US first class mail; $2 check 5. US first class mail; $5 check | |
| Outcomes | Response period not specified | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | All subjects received a pre‐notification letter; Age: Mostly 40‐49 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Doody 2003b.
| Methods | Random allocation: method not specified | |
| Data | US radiologist technologists who had not responded to 2 earlier mailings of a questionnaire | |
| Comparisons | 1. Federal express; No incentive 2. Federal express; $1 bill 3. Federal express; $2 bill 4. Federal express; $2 check | |
| Outcomes | Response period not specified | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly 40‐49 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dorman 1997.
| Methods | Random allocation: using an allocation code generated by an adaptive randomisation algorithm | |
| Data | Patients who had been entered into the International stroke trial between 2 March 1993 and 31 may 1995 | |
| Comparisons | 1. Questionnaire incorporating the EuroQol
2. Questionnaire incorporating the SF‐36 Questionnaires were identical in all respects other than the nature of the HRQoL instrument. EuroQol has 7 questions, SF‐36 has 36. Both had same number of pages, but the first questionnaire had fewer questions Reminders sent to non‐responders after 2 weeks |
|
| Outcomes | — | |
| Topic | Health : SF‐36, Euro QoL | |
| Mode of Administration | Postal | |
| Notes | The randomisation algorithm used aimed to balance the 2 groups for age, sex, stroke syndrome and the time from stroke onset to follow up | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Downes‐Le Guin 2002.
| Methods | Random allocation: using random number generation | |
| Data | IT managers in US businesses | |
| Comparisons | 1. Unconditional Amazon gift certificate ($15) 2. Unconditional Amazon gift certificate ($25) 3. Conditional Amazon gift certificate ($15) 4. Conditional Amazon gift certificate ($25) |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Drummond 2008.
| Methods | Random allocation: using random number generation | |
| Data | Primary care physicians working in Ireland | |
| Comparisons | 1. Pre‐contact via mail 2. No pre‐contact 3. Questionnaire order: Version 1, demographics first 4. Questionnaire order: Version 2, topic specific questions first (Prostate‐specific antigen testing) |
|
| Outcomes | Response period not specified | |
| Topic | Health: Views and practices about prostate‐specific testing (PSA) | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Duffy 2001.
| Methods | Random allocation: Twin numbered 01 in each pair received single stamp, the other received the intervention | |
| Data | Twins who are volunteer members of the Australian NHMRC Twin Registry | |
| Comparisons | 1. Single stamp on enclosed return envelope 2. Multiple stamps (3‐5) on enclosed return envelope | |
| Outcomes | Response period not specified | |
| Topic | Health: Asthma, Psoriasis | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Duhan 1990.
| Methods | Random allocation: method not specified | |
| Data | Industrial marketing executives | |
| Comparisons | 1. Pre‐notification 2. No prior notification | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Dunn 2003.
| Methods | Random allocation: using random number generation | |
| Data | Patients aged 30‐59 years with back pain in the UK | |
| Comparisons | 1. Traditional questionnaire ‐ Generic questionnaires first followed by disease‐specific ones 2. Chronological questionnaire ‐ Individual questions arranged in sections according to the period of time that they ask about |
|
| Outcomes | Response period not specified | |
| Topic | Health: Patient‐base outcome measures ‐ Chronic pain grade, SF‐36, Hospital & Anxiety Scale, Roland‐Morris Disability Questionnaire | |
| Mode of Administration | Postal | |
| Notes | Me an age: 45 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Eaker 1998.
| Methods | Random allocation: method not specified | |
| Data | Men and women living in Sweden in 1995 | |
| Comparisons | 1. Preliminary notification (PN); Long questionnaire (LQ); Mention of telephone contact (MTC)
2. PN; Short questionnaire (SQ); MTC
3. PN; LQ; No MTC
4. PN; SQ; No MTC
5. No PN; LQ; MTC
6. No PN; SQ; No MTC
7. No PN; LQ; No MTC
8. No PN; SQ; No MTC Reminders sent to all after 1 week |
|
| Outcomes | Response within 75 days | |
| Topic | Health: Medical history, physical activity, eating and drinking habits, reproductive history | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly above 45 years; Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Easton 1997.
| Methods | Random allocation: method not specified | |
| Data | Paediatricians listed in the American Academy of Paediatrics Directory | |
| Comparisons | 1. Information booklet 2. $1 incentive | |
| Outcomes | Response period not specified | |
| Topic | Health: Counselling about sun protection | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Edwards 2001.
| Methods | Random allocation: central randomisation | |
| Data | Head injured adults in the CRASH trial (UK) | |
| Comparisons | 1. 1‐page questionnaire 2. 3‐ page questionnaire | |
| Outcomes | Response within 3 months | |
| Topic | Health: Disability after traumatic brain injury | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Elkind 1986.
| Methods | Random allocation: using alternation | |
| Data | Psychologists with APA membership | |
| Comparisons | 1. Plain covering envelope with rubber‐stamped return address 2. University‐printed envelope 3. Postage‐stamped 4. Business reply |
|
| Outcomes | 1. Response rate at 6 weeks 2. Response rate after 12 weeks |
|
| Topic | Health: Patients' violence and harassment | |
| Mode of Administration | Postal: first class mail | |
| Notes | Method confirmed by the author; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Enger 1993.
| Methods | Random allocation: method not specified | |
| Data | College graduates | |
| Comparisons | 1. 2‐ page questionnaire; Stamped return envelope 2. 1‐page questionnaire; Stamped return envelope 3. 1‐page questionnaire designed as a self‐mailer | |
| Outcomes | Response period not specified | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Erdogan 2002.
| Methods | Random allocation: systematic assignment | |
| Data | Advertising agency managers who had not responded to a questionnaire mailed 2 weeks previous | |
| Comparisons | 1. Original replacement follow‐up mailing: A colour department‐headed cover letter, original questionnaire plus self addressed, first class stamped return envelope 2. Photocopy replacement follow‐up mailing: A colour department‐headed cover letter, photocopied questionnaire plus self addressed, first class stamped return envelope 3. Post card: Colour departmental follow up postcard only 4. Letter: Colour department headed follow up letter only | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Etter 1996.
| Methods | Random allocation: computerised random number generation | |
| Data | French‐speaking patients at a medical practice in the suburbs of Geneva who had recently consulted a physician and who lived in Geneva at the time of data collection | |
| Comparisons | 1. University letterhead; Cover letter signed by the researchers; Business reply envelope addressed to the University of Geneva
2. Medical Practice letterhead; Cover letter signed by the director of the medical practice; Business reply envelope addressed to the practice Packages sent to non‐respondents every 10 days up to a maximum of 4 times Reminder postcards sent 2 days after first and second mailings |
|
| Outcomes | Response within 45 days | |
| Topic | Health: Patient satisfaction | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Etter 1998a.
| Methods | Random allocation: computerised random number generation | |
| Data | Students, faculty, administrative and technical staff of a university (Geneva, Switzerland) | |
| Comparisons | 1. Sent saliva vial; Offered participation in lottery; Pen incentive
2. Saliva vial; Pen incentive
3. Saliva vial; Offered participation in lottery
4. Saliva vial
5. Offered participation in lottery; Pen incentive
6. Pen incentive
7. Offered participation in lottery
8. None Best response intervention was sent as follow up |
|
| Outcomes | — | |
| Topic | Health: Health status using SF‐36, smoking habits, self‐efficacy | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Mean age: 28.5 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Etter 1998b.
| Methods | Random allocation: computerised random number generation | |
| Data | Residents of Geneva | |
| Comparisons | 1. Professional layout; Prior feedback letter 2. Professional layout; No prior feedback letter 3. Standard layout; Prior feedback letter 4. Standard layout; Prior feedback letter | |
| Outcomes | — | |
| Topic | Health: Use of health services, satisfaction with medical care | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Mean age: 32 years; Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Etter 2002.
| Methods | Random allocation: method not specified | |
| Data | Members of various health insurance plans aged 19‐45 (Geneva, Switzerland) | |
| Comparisons | 1. Light green paper questionnaire
2. White paper questionnaire 5 follow‐up reminder questionnaires were used |
|
| Outcomes | Response within 50 days | |
| Topic | Health: Health status, health related life styles, use of medical services, satisfaction with medical care, socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | Age: 19‐45 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Etzel 1974.
| Methods | Random allocation: method not specified | |
| Data | Random sample of bank credit card holders on a list provided by a bank, USA | |
| Comparisons | 1. No follow up 2. Follow‐up without duplicate questionnaire and return envelope sent 5 days after initial mailing 3. Follow‐up with duplicates sent 5 days after initial mailing | |
| Outcomes | Response within 17 days | |
| Topic | Non‐health: Finance ‐ Credit care usage | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Evans 2004.
| Methods | Random allocation: method not specified | |
| Data | Men diagnosed with Prostate cancer | |
| Comparisons | 1. Unconditional 30 minutes prepaid phone card 2. Conditional 30 minutes prepaid phone card |
|
| Outcomes | Response period not specified | |
| Topic | Health: Dietary supplementation use in cancer patients | |
| Mode of Administration | Postal | |
| Notes | Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Falthzik 1971.
| Methods | Random allocation: odd numbered firms received closed question, even numbered firms received open‐ended question | |
| Data | Personnel departments of 200 firms listed in Fortune magazine's list of the 500 largest firms in the US | |
| Comparisons | 1. Closed question 2. Open‐ended question | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Characteristics while hiring college graduates | |
| Mode of Administration | Postal | |
| Notes | Random allocation unclear | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Faria 1990.
| Methods | Random allocation: alternation | |
| Data | Homeowners residing in a medium sized US city on the 'city property owners' listing | |
| Comparisons | 1. Telephone pre‐contact 1‐3 days before questionnaire mailing 2. Letter pre‐notification sent 2 days before questionnaire mailing 3. No pre‐contact | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Faria 1992.
| Methods | Random allocation: alternation | |
| Data | Individuals listed on the company mailing list of a major manufacturer | |
| Comparisons | 1. University sponsor; No promised contribution to charity 2. University sponsor; Promised contribution to a specified charity 3. University sponsor; Promised contribution to 1 of 3 charities selected by respondent 4. Commercial sponsor; No promised contribution to charity 5. Commercial sponsor; Promised contribution to charity 6. Commercial sponsor; Promised contribution to 1 of 3 charities selected by respondent | |
| Outcomes | Response within 23 days | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Faria 1997.
| Methods | Random allocation: method not specified | |
| Data | Patients with acute stroke | |
| Comparisons | 1. Questionnaire with stamped return envelope 2. Questionnaire with free post return envelope | |
| Outcomes | — | |
| Topic | Health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Feild 1975.
| Methods | Random allocation: method not specified | |
| Data | Full‐time teaching faculty members of a large southeastern university (US) | |
| Comparisons | 1. Signed by male investigator; Sent to male subject 2. Signed by male investigator; Sent to female subject 3. Signed by female investigator; Sent to male subject 4. Signed by female investigator; Sent to female subject 5. Signed by both male and female investigators; Sent to male subject 6. Signed by both male and female investigators; Sent to female subject | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Short form of the attitudes towards women scale | |
| Mode of Administration | Postal | |
| Notes | Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ferrell 1984.
| Methods | Random allocation: method not specified | |
| Data | Practitioners in managerial or administrative capacities listed in the American Marketing Association roster | |
| Comparisons | 1. Questionnaire sent to home address 2. Questionnaire sent to work address | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Marketing terms used by organisations, description of jobs, and their firm | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Finn 1983.
| Methods | Random allocation: method not specified | |
| Data | Heads of households in the trading area of certain financial institutions. The target area was a middle to high income section of the city and included all age groups and family sizes | |
| Comparisons | 1. Return envelope with standard first class stamp and typed return address 2. Pre‐printed business reply envelope | |
| Outcomes | Response within 29 days | |
| Topic | Non‐health: Finance ‐ Usage of financial institutions, attitudes about local banks, savings and loan associations | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Finsen 2006.
| Methods | Random allocation: alphabetical order | |
| Data | Norwegian residents aged between 40 and 65 years | |
| Comparisons | 1. Unconditional; 1 scratch lottery worth 20 Norwegian Kroner (NOK) 2. Unconditional; 2 scratch lotteries each worth 20 Norwegian Kroner 3. Conditional; 2 scratch lotteries each worth 20 Norwegian Kroner on reply within one week 4. Unconditional; 50 NOK 5. Control |
|
| Outcomes | Response rate at 6 week | |
| Topic | Health: History of surgeries | |
| Mode of Administration | Postal | |
| Notes | Age: 51.4 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Fiset 1994.
| Methods | Random allocation: alternation | |
| Data | Dentists insured by a major malpractice carrier in 2 western states (US) | |
| Comparisons | Experiment 1:
1. $5 incentive
2. $10 incentive
Follow‐up with postcard after 1 week Experiment 2: 1. $5 incentive 2. $10 incentive Follow‐up with postcard after 1 week Questionnaire package sent to non‐responders again at 3 and 7 weeks |
|
| Outcomes | Response period not specified | |
| Topic | Health: Dentist relationship of dental malpractice claims to decisions about clinical practice | |
| Mode of Administration | Postal | |
| Notes | Mean age: 37‐41.4 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Ford 1967a.
| Methods | Random allocation: method not specified | |
| Data | Residents of Chenoa | |
| Comparisons | 1. Advance letter 2. No advance letter | |
| Outcomes | Response within 30 days | |
| Topic | Non‐health: Consumer shopping survey | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ford 1967b.
| Methods | Random allocation: method not specified | |
| Data | Residents of Beardstown | |
| Comparisons | 1. Advance letter 2. No advance letter | |
| Outcomes | Response within 30 days | |
| Topic | Non‐health: Consumer shopping survey | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ford 1968.
| Methods | Random allocation: method not specified | |
| Data | Households | |
| Comparisons | 1. Questionnaire consisted of
1 sheet, printed on both sides which when folded had four 8.5 x 11" pages of questions
2. Questionnaire mimeographed on 1 side only and stapled so had four pages of 8.5 x 14" All participants were sent an advance letter 12 days before the questionnaire was sent |
|
| Outcomes | Response within 23 days | |
| Topic | Non‐health: Consumer shopping survey | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Foushee 1990.
| Methods | Random allocation: using random number generation in SAS | |
| Data | Tour operators in Europe, South America, and Japan | |
| Comparisons | 1. Early follow up with post card (3 weeks) 2. Late follow up with post card (6 weeks) |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Potential for attracting and accommodating foreign visitors to national park | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate. |
Freise 2001.
| Methods | Random allocation: using dice | |
| Data | Last 1400 discharged patients of the University hospital of Cologne on 14/02/2000 | |
| Comparisons | 1. 12 page questionnaire 2. 8 page questionnaire 3. 4 page questionnaire |
|
| Outcomes | Response period not specified | |
| Topic | Health: Cologne patient questionnaire | |
| Mode of Administration | Postal | |
| Notes | Age: Above 18 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Friedman 1975.
| Methods | Random allocation: method not specified | |
| Data | Travel agents who subscribed to a travel magazine | |
| Comparisons | 1. Author had 'Hispanic' name 2. Author had 'Jewish' name 3. Ethnicity of author not identifiable | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Ethnic identification | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Friedman 1979.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in telephone directories of 2 suburban areas in the greater New York Metropolitan area | |
| Comparisons | 1. Black sponsor signature; 25 cents incentive 2. Black sponsor signature; No incentive 3. White sponsor signature; 25 cents incentive 4. White sponsor signature; No incentive | |
| Outcomes | Response within 2 weeks | |
| Topic | Non‐health: Attitudes towards the Negroes Scale | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Furse 1982.
| Methods | Random allocation: method not specified | |
| Data | Microwave oven owners listed in a major manufacturer's warranty registration records | |
| Comparisons | 1. No personal or charity incentive offered 2. Charity incentive (promise of $1 to charity of respondent's choice for returned questionnaire) 3. 50 cents enclosed with questionnaire 4. $1 enclosed with questionnaire 5. 50 cents enclosed with questionnaire and charity incentive (promise of $1 to charity of respondent's choice for returned questionnaire) 6. $1 enclosed with questionnaire and charity incentive (promise of $1 to charity of respondent's choice for returned questionnaire) | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Furst 1979.
| Methods | Random allocation: computerised random number generation | |
| Data | Secretaries of school principals | |
| Comparisons | 1. Pre‐notification 2. No pre‐notification | |
| Outcomes | Response period not specified | |
| Topic | Health: Eysenck Personality Inventory (EPI) | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author. Informed that allocation concealment was poor | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Futrell 1977.
| Methods | Random allocation: method not specified | |
| Data | Salesmen from a national hospital supply company | |
| Comparisons | 1. Instruction to return the questionnaire unsigned
2. Asked to sign the questionnaire 2 follow‐up letters sent 10 days apart 2 weeks after questionnaire sent |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Salesman's attitudes towards their job, evaluation of job performance by supervisors | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Futrell 1978.
| Methods | Random allocation: method not specified | |
| Data | Grocery store managers | |
| Comparisons | 1. Allowed to remain anonymous 2. Required to sign questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Job attitudes | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Futrell 1981.
| Methods | Random allocation: method not specified | |
| Data | Farmers and ranchers | |
| Comparisons | 1. Questionnaire and letter 2. Questionnaire and letter; Non‐respondents after 2 weeks sent letter and questionnaire 3. Questionnaire and letter; Non‐respondents after 2 weeks sent letter only 4. Questionnaire and letter; Non‐respondents after 2 and 4 weeks sent letter and questionnaire 5. Questionnaire and letter; Non‐respondents after 2 and 4 weeks sent letter only 6.Questionnaire and letter; Non‐respondents after 2, 4 and 6 weeks sent letter and questionnaire 7. Questionnaire and letter; Non‐respondents after 2, 4 and 6 weeks sent letter only | |
| Outcomes | — | |
| Topic | Non‐health: Finance ‐ Perceptions of agricultural producers regarding financial lending institutions | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Futrell 1982.
| Methods | Random allocation: method not specified | |
| Data | Industrial accountants | |
| Comparisons | 1. No statement assuring anonymity; Asked to return questionnaire the same day it was received 2. No statement assuring anonymity; Asked to return questionnaire at their leisure 3. Statement assuring anonymity; Asked to return questionnaire the same day it was received 4. Statement assuring anonymity; Asked to return questionnaire at their leisure | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Role conflict, role clarity, job tension, job satisfaction | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gajraj 1990.
| Methods | Random allocation: alternation | |
| Data | Customers of a major public utility, comprising households in south‐western Ontario | |
| Comparisons | 1. No incentive
2. $0.50 included
3. Promise of $0.50 on return of completed questionnaire
4. Pen included
5. Promise of pen on return of completed questionnaire
6. Inclusion in share of winning from 5 Super Lotto lottery tickets
7. Promise of inclusion in share of 5 Super Lotto lottery tickets on return of completed questionnaire All sent same questionnaire, mailing envelope, computer printed label and return envelope. Cover letters varied only in stating amount of incentive |
|
| Outcomes | Response within 25 days | |
| Topic | Non‐health: General area of energy conservation | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author. Informed that allocation concealment was adequate | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Gaski 2004a.
| Methods | Random allocation: using coin toss | |
| Data | US "Mass‐market" dealers of the Gillette company's paper mate division | |
| Comparisons | 1. Dissertation referencing in the cover letter 2. No dissertation referencing in the cover letter |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Behavioural relations between manufacturer and its distributor | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Gaski 2004b.
| Methods | Random allocation: using coin toss | |
| Data | Wholesalers serving stationery/ office supply and school supply stores | |
| Comparisons | 1. Dissertation referencing in the cover letter 2. No dissertation referencing in the cover letter |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Behavioural relations between manufacturer and its distributor | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Gattellari 2001.
| Methods | Random allocation: computerised random number generation | |
| Data | All active fellows of the Royal Australasian College of Surgeons (RACS) | |
| Comparisons | 1. Promise of a $A10 donation to RACS for every returned questionnaire 2. No offer of donation | |
| Outcomes | Response period not specified | |
| Topic | Health: Need for evidence‐based clinical practice guidelines for the management of colorectal cancer | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Gattellari 2004.
| Methods | Random allocation: using block randomisation | |
| Data | Men from general practice surgeries in Sydney, Australia | |
| Comparisons | 1. Mention of deadline to return the questionnaire within 1 week 2. No mention of deadline |
|
| Outcomes | Response period not specified | |
| Topic | Health: Prostate cancer screening | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Gendall 1996.
| Methods | Random allocation: using alternation | |
| Data | New Zealanders aged 18 and above, selected from the New Zealand electoral rolls | |
| Comparisons | 1. Cover with simple graphic design in black letters 2. Cover with complex design in black and red letters 3. Cover with different complex design in black and red letters 4. Inclusion of a picture or a photo 5. Without a picture or a photo |
|
| Outcomes | Response rate at 12 weeks | |
| Topic | Health: Demography ‐ Family and changing gender roles | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Gendall 1998.
| Methods | Random allocation: method not specified | |
| Data | Individuals on the electoral roll (New Zealand) | |
| Comparisons | 1. Control
2. High quality foil‐wrapped tea bag included
3. $1 coin included 2 follow up s sent |
|
| Outcomes | — | |
| Topic | Non‐health: Role of government, attitudes to work orientations | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gendall 2005a.
| Methods | Random allocation: using alternation | |
| Data | New Zealanders aged 18 and above, selected from the New Zealand electoral rolls | |
| Comparisons | 1. Personalised cover letter 2. Non‐personalised cover letter |
|
| Outcomes | Response period not specified | |
| Topic | Health: Environmental issues, demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gendall 2005b.
| Methods | Random allocation: using alternation | |
| Data | New Zealanders aged 18 and above, selected from the New Zealand electoral rolls | |
| Comparisons | 1. Cover design ‐ Circle 2. Cover design ‐ Blocks 3. Cover design ‐ No graphics |
|
| Outcomes | Response period not specified | |
| Topic | Health: Demographics, disability issues, families and friends, experiences of funerals | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gendall 2005c.
| Methods | Random allocation: using alternation | |
| Data | New Zealanders aged 18 and above, selected from the New Zealand electoral rolls | |
| Comparisons | 1. Two 45‐cent postage stamp 2. Foil‐wrapped dilmah tea bag 3. Small foil‐wrapped gold coin with a 20 cent denomination 4. Large foil‐wrapped gold coin with either a 50 cent or $2 denomination 5. No incentives |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Citizenship in New Land | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gibson 1999a.
| Methods | Random allocation: randomisation sequence generated using random number function on SAS | |
| Data | Medicaid subjects from families that included at least 1 member who had been enrolled continuously in the respective programme from July‐Dec 1993 | |
| Comparisons | 1. Medicaid; No incentive
2. Medicaid; $1 incentive
3. Medicaid; $2 incentive
4. Basic Health Plan; No incentive
5. Basic Health Plan; $1
6. Basic Health Plan; $2 Non‐respondents after second mailing were randomised to receive third mailing by certified mail or by 2‐day priority mail |
|
| Outcomes | — | |
| Topic | Health: Access and use of health services, demographics | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. No information on allocation concealment provided | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gibson 1999b.
| Methods | Random allocation: randomisation sequence generated using random number function on SAS | |
| Data | BHP subjects from all families that included at least 1 member who had been enrolled continuously in the respective programme from July‐Dec 1993 | |
| Comparisons | 1. Medicaid; No incentive
2. Medicaid; $1 incentive
3. Medicaid; $2 incentive
4. Basic Health Plan; No incentive
5. Basic Health Plan; $1
6. Basic Health Plan; $2 Non‐respondents after second mailing were randomised to receive third mailing by certified mail or by 2‐day priority mail |
|
| Outcomes | — | |
| Topic | Health: Access to health services, use of services, satisfaction with services, demographics | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. No information on allocation concealment provided. | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gibson 1999c.
| Methods | Random allocation: randomisation sequence generated using random number function on SAS | |
| Data | Non‐responding Medicaid subjects from families that included at least 1 member who had been enrolled continuously in the respective programme from July‐Dec 1993 | |
| Comparisons | 1. Certified mail 2. 2‐day priority mail | |
| Outcomes | — | |
| Topic | Health: Access and use of health services, demographics | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. No information on allocation concealment provided | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Giles 1978.
| Methods | Random allocation: method not specified | |
| Data | Faculty members | |
| Comparisons | 1. Combination format (CombF); Satisfaction items first (S1st);
2 demographic items (DI)
2. CombF; S1st; 4DI
3. CombF; S1st; 6DI
4. CombF; S1st; 8DI
5. CombF; S1st; 10DI
6. CombF; Demographic items first (D1st); 2DI
7. CombF; D1st; 4DI
8. CombF; D1st; 6DI
9. CombF; D1st; 8DI
10. CombF; D1st; 10DI
11. Categorical Format (CategF); S1st; 2DI
12. CategF; S1st; 4DI
13. CategF; S1st; 6DI
14. CategF; S1st; 8DI
15. CategF; S1st; 10DI
16. CategF; D1st; 2DI
17. CategF; D1st; 4DI
18. CategF; D1st; 6DI
19. CategF; D1st; 8DI
20. CategF; D1st; 10DI No follow up s used |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Job satisfaction | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gillpatrick 1994.
| Methods | Random allocation: method not specified | |
| Data | Engineers identified from the subscriber list of a major trade journal | |
| Comparisons | 1. $1 incentive 2. No incentive 3. Pre‐contact 4. No pre‐contact | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Market perceptions about CAD workstations | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gitelson 1992.
| Methods | Random allocation: method not specified | |
| Data | Spectators at the Pennsylvania Farm Show who had not responded to 3 previous mailings of the questionnaire | |
| Comparisons | 1. Non‐personalised questionnaire; Regular post 2. Personalised questionnaire; Regular post 3. Personalised questionnaire; Certified post | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Economic impact of the farm show | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Glisan 1982.
| Methods | Random allocation: method not specified | |
| Data | Farmers from 6 geographical regions | |
| Comparisons | 1. Incentive ‐ monetary 2. Incentive ‐ results promised 3. Incentive ‐ control 4. Colour ‐ tan 5. Colour ‐ blue 6. Colour ‐ white 7. Stamp ‐ commemorative 8. Stamp ‐ regular | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Farm operations and costs | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Godwin 1979.
| Methods | Random allocation: method not specified | |
| Data | Individuals in 60 countries | |
| Comparisons | 1. No incentive
2. $25
3. $50 Participants were requested to return the questionnaire within 3 weeks. After 2 weeks a single follow‐up letter with a copy of the questionnaire was sent to all respondents |
|
| Outcomes | Response period not specified | |
| Topic | Health: Family planning programmes | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Goldstein 1975.
| Methods | Random allocation: method not specified | |
| Data | Subscribers to a travel magazine | |
| Comparisons | 1. Postcard format first wave; Postcard format second wave 2. Form first wave; Form second wave 3. Postcard format first wave; Form second wave 4. Form first wave; Postcard format second wave | |
| Outcomes | Response period not specified | |
| Topic | Non‐health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Goodstadt 1977.
| Methods | Random allocation: method not specified | |
| Data | Readers of Addictions Magazine | |
| Comparisons | 1. 25 cent incentive 2. Free book incentive 3. Promise of free book 4. No incentive | |
| Outcomes | — | |
| Topic | Non‐health: Reading habits, magazine function served, the range and depth of subjects covered, overall design | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Green 1986.
| Methods | Random allocation: method not specified | |
| Data | Teachers chosen from the Wyoming State Department of Education list of educators | |
| Comparisons | 1. Personalised cover letter 2. Non‐personalised cover letter |
|
| Outcomes | — | |
| Topic | Non‐health: Courses taken in tests and measurement, attitudes towards standardised and classroom testing, interest in topics for in service training | |
| Mode of Administration | Postal | |
| Notes | Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Green 1989.
| Methods | Random allocation: method not specified | |
| Data | In‐service teachers from the states of Wyoming and Nebraska | |
| Comparisons | 1. Offer of a summary of results vs none 2. Personalisation vs No personalisation | |
| Outcomes | — | |
| Topic | Non‐health: Application of research methods and findings to classroom teaching | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Green 2000.
| Methods | Random allocation: method not specified | |
| Data | Randomly selected US social workers | |
| Comparisons | 1. Demographic items placed at the beginning of the questionnaire 2. Demographic items placed at the end of the questionnaire | |
| Outcomes | — | |
| Topic | Health: Attitudes and beliefs about roles of family interaction and biological factors in mental illness | |
| Mode of Administration | Postal | |
| Notes | Mean age: 44.5 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Greer 1994.
| Methods | Random allocation: method not specified | |
| Data | Senior sales executives (US) | |
| Comparisons | 1. University sponsor; White questionnaire
2. University sponsor; Yellow questionnaire
3. University sponsor; Pink questionnaire
4. University sponsor; Green questionnaire
5. Commercial research sponsor; White questionnaire
6. Commercial research sponsor; Yellow questionnaire
7. Commercial research sponsor; Pink questionnaire
8. Commercial research sponsor; Green questionnaire
9. Academic honour society sponsor; White questionnaire
10. Academic honour society sponsor; Yellow questionnaire
11. Academic honour society sponsor; Pink questionnaire
12. Academic honour society sponsor; Green questionnaire
13. No sponsor (PO Box); White questionnaire
14. No sponsor (PO Box); Yellow questionnaire
15. No sponsor (PO Box); Pink questionnaire
16. No sponsor (PO Box); Green questionnaire Follow up sent after 3 weeks |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Company's programme for sales people | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Griffith 1999.
| Methods | Random allocation: method not specified | |
| Data | General medical internists in 5 Canadian provinces | |
| Comparisons | 1. Open‐ended questionnaire format 2. Close‐ended questionnaire format | |
| Outcomes | — | |
| Topic | Health: Career satisfaction | |
| Mode of Administration | Postal | |
| Notes | Mean age: 51.9 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Groeneman 1986.
| Methods | Random allocation: method not specified | |
| Data | People listed in the telephone directories of Toronto, Montreal, Vancouver and Winnipeg, Canada selected using 'distinctive Jewish name sampling' | |
| Comparisons | 1. $1 bill enclosed 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Travel experience and attitudes towards future trips | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Groves 2000.
| Methods | Random allocation: method not specified | |
| Data | Therapeutic recreation co‐ordinators in the US | |
| Comparisons | 1. Stamped addressed return envelope included 2. Self‐adhering return address level (no envelope or postage) included | |
| Outcomes | Response period not specified | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gueguen 2003a.
| Methods | Random allocation: using random number generation | |
| Data | University students. | |
| Comparisons | 1. Attractive photo in the e‐mail 2. Medium attractive photo in the e‐mail 3. No photo in the e‐mail 4. Male signature 5. Female signature |
|
| Outcomes | Response period not specified | |
| Topic | Health: Dietary habits | |
| Mode of Administration | Electronic: E‐mail | |
| Notes | Equal males and females; Language of publication is French | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Gueguen 2003b.
| Methods | Random allocation: using random number generation | |
| Data | Sample of individuals with e‐mail addresses ending in ".fr" picked up randomly from the Internet using a specialised software | |
| Comparisons | 1. Attractive photo in the e‐mail 2. Medium attractive photo in the e‐mail 3. Less attractive photo in the e‐mail 4. No photo in the e‐mail 5. Male signature 6. Female signature |
|
| Outcomes | Response period not specified | |
| Topic | Health: Dietary habits | |
| Mode of Administration | Electronic: E‐mail | |
| Notes | Language of publication is French | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Gullahorn 1959.
| Methods | Random allocation: method not specified | |
| Data | Former Fulbright & Smith‐Mundt grantees who had not responded to earlier mailing of the questionnaire | |
| Comparisons | 1. Follow‐up mailings by special delivery 2. Follow‐up mailings by standard mail | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Bibliography of works emanating form Fulbright and Smith‐Mundt awards | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gullahorn 1963.
| Methods | Random allocation: method not specified | |
| Data | Former Fulbright and Smith‐Mundt grantees | |
| Comparisons | 1. Questionnaire printed on green paper, sent by first class mail, with business reply return envelope 2. Green paper; first class, stamped return envelope 3. Green paper, third class mail, business reply return envelope 4. Green paper, third class mail, return envelope stamped 5. White paper, first class mail, business reply return envelope 6. White paper, first class, return envelope stamped 7. White paper, third class mail, business reply return envelope 8. White paper, third class mail, return envelope stamped | |
| Outcomes | — | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Gupta 1997.
| Methods | Random allocation: method not specified | |
| Data | Medical practitioners | |
| Comparisons | 1. Telephone prompt by medical researcher 2. Telephone prompt by an experienced non‐medical research assistant | |
| Outcomes | — | |
| Topic | Health: Views about clinical practice guidelines | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Göritz 2004a.
| Methods | Random allocation: using computerised random number generation | |
| Data | Panellists from the German commercial online access panel | |
| Comparisons | 1. 7 X 100 (700) German Mark (DM) money lottery 2. 14 X 50 (700) DM money lottery 3. 5 X 100 (500) DM money lottery 4. 10 X 50 (500) DM money lottery 5. 3 X 100 (300) DM money lottery 6. 6 X 50 (300) DM money lottery 7. 1 X 100 (100) DM money lottery 8. 2 X 50 (100) DM money lottery 9. 8 Bonus Point (BP) (1 BP is worth 50 DM) 10. 6 BP 11. 4 BP 12. 3 BP 13. Gift lottery (3 watches/5 CD‐jackets/5 alarm clocks/25 key‐ring torches). |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Personal Internet usage | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Göritz 2004b.
| Methods | Random allocation: using computerised random number generation | |
| Data | Panellists from the German commercial online access panel | |
| Comparisons | 1. 2 X 90 (180) German Mark (DM) 2. 6 X 30 DM money lottery 3. 1 X 90 DM money lottery 4. 3 X 30 DM money lottery |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Evaluation of media contents | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Hackler 1973.
| Methods | Random allocation: alternation | |
| Data | Mothers of ninth or tenth grade students living in 1 neighbourhood of Edmonton | |
| Comparisons | 1. No incentive
2. $1 bill incentive After 11 days, the no incentive group received $1 and the incentive group received a follow‐up phone call |
|
| Outcomes | — | |
| Topic | Non‐health: Community cohesiveness | |
| Mode of Administration | Postal | |
| Notes | Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Halpern 2002.
| Methods | Random allocation: method not specified | |
| Data | General internists and family practitioners randomly selected from the American Medical Association's master file of physicians | |
| Comparisons | 1. $10, peppermint candy and large outgoing envelope 2. $10, no peppermint candy, large outgoing envelope 3. $10, peppermint candy, small outgoing envelope 4. $10, no peppermint candy, small outgoing envelope 5. $5, peppermint candy and large outgoing envelope 6. $5, no peppermint candy, large outgoing envelope 7. $5, peppermint candy, small outgoing envelope 8. $5, no peppermint candy, small outgoing envelope | |
| Outcomes | Response within 11 weeks | |
| Topic | Health: Views about comparative merits of placebo controlled versus active controlled trials of anti‐hypertensive drugs | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hancock 1940.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed on the personal tax records of the county assessors | |
| Comparisons | 1. Questionnaire and cover letter 2. As above with 25 cents incentive 3. As above with promise of 25 cents on return of questionnaire 4. Personal interview | |
| Outcomes | Response period not specified | |
| Topic | — | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hansen 1980.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in the telephone directory (Columbus, Ohio) | |
| Comparisons | 1. No pre‐contact; Short form (SF) 2. No pre‐contact; Long form (LF) 3. Yes/no foot in the door; SF 4. Yes/no foot in the door; LF 5. Probe foot in the door; SF 6. Probe foot in the door; LF | |
| Outcomes | Response within 35 days | |
| Topic | Non‐health: Consumer's attitudes towards recent new car purchases. CHECK | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hansen RA 1980.
| Methods | Random allocation: method not specified | |
| Data | Safety engineers employed by firms that require employees to wear safety hardhats | |
| Comparisons | 1. 25 cent incentive 2. Pen incentive 3. Control group | |
| Outcomes | Response within 38 days | |
| Topic | Non‐health: Product evaluation and information | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Harris 1978.
| Methods | Random allocation: method not specified | |
| Data | A randomly selected sample of respondents | |
| Comparisons | 1. Business reply return envelope enclosed 2. Stamped reply envelope enclosed | |
| Outcomes | Response within 4 weeks | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Harrison 2002.
| Methods | Random allocation: computerised random number generation | |
| Data | Adults selected from a Health Authority Register (North West England) | |
| Comparisons | 1. Reply envelope with first class stamp 2. Pre‐paid business‐franked reply envelope | |
| Outcomes | — | |
| Topic | Health: Health questionnaire | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly 18‐45 years; Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Harrison 2004.
| Methods | Random allocation: using random number generation | |
| Data | Patients referred to a community based exercise referral scheme | |
| Comparisons | 1. Pre‐warning latter 2.No pre‐warning letter |
|
| Outcomes | Response rate at 6 weeks | |
| Topic | Health: Quality of services offered at the community based referral scheme | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Harvey 1986.
| Methods | Random allocation: alternation | |
| Data | A random sample of people living in the West Midlands, UK, listed on the electoral register | |
| Comparisons | 1. Reply envelope with first class stamp 2. Reply envelope with second class stamp | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Interest in fine art | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Hawkins 1979.
| Methods | Random allocation: method not specified | |
| Data | Eugene residences listed in the Eugene‐Springfield telephone director | |
| Comparisons | 1. Department store sponsor; Standard 2. Department store sponsor; Disclosure 3. Research firm sponsor; Standard 4. Research firm sponsor; Disclosure 5. University sponsor, Standard 6. University sponsor, Disclosure | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Women's attitudes to shopping, demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Heaton 1965.
| Methods | Random allocation: method not specified | |
| Data | Individuals living in the Philadelphia, Pennsylvania area who had purchased a new 1959 Chevrolet within the previous 12‐16 weeks | |
| Comparisons | 1. Preliminary letter 2. No preliminary letter | |
| Outcomes | Response within 2 weeks | |
| Topic | Non‐health: Information on automobile ownership, shopping behaviour | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Heerwegh 2005a.
| Methods | Random allocation: using SAS RANUNI function | |
| Data | 1st year students at the Katholieke Universiteit Leuven, Belgium | |
| Comparisons | 1. Personalised salutations 2. Non‐personalised salutations |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Adolescents attitudes towards marriage and divorce | |
| Mode of Administration | Electronic: Web survey | |
| Notes | Method of allocation ascertained through contact with author; Age: 17‐20 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate. |
Heerwegh 2005b.
| Methods | Random allocation: using SAS RANUNI function | |
| Data | 1st year students at the Katholieke Universiteit Leuven, Belgium | |
| Comparisons | 1. Personalised salutations 2. Non‐personalised salutations |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Adolescents attitudes towards marriage and divorce | |
| Mode of Administration | Electronic: Web survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Heerwegh 2006.
| Methods | Random allocation: using SAS RANUNI function | |
| Data | Freshmen at the Katholieke Universiteit Leuven, Belgium | |
| Comparisons | 1. Personalised salutations 2. Non‐personalised salutations |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes towards immigrants and asylum seekers | |
| Mode of Administration | Electronic: Web survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate. |
Hendrick 1972.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in the city directory (Akron, Ohio) | |
| Comparisons | 1. 1‐page questionnaire; Solicitor ingratiate (SI); Respondent ingratiate (RI) 2. 1‐page questionnaire, SI; Respondent no ingratiate (RNI) 3. 1‐page questionnaire; Solicitor no ingratiate (SNI); RI 4. 1‐page questionnaire; SNI; RNI 5. 7‐page questionnaire; SI; RI 6. 7‐page questionnaire; SI; RNI 7. 7‐page questionnaire; SNI; RI 8. 7‐page questionnaire; SNI; RNI | |
| Outcomes | — | |
| Topic | Health: Repression ‐ sensitis ation personality scale | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hendriks 2001.
| Methods | Random allocation: alternation | |
| Data | 784 consecutively discharged patients from 8 randomly chosen hospital wards at the Academic Medical Center, Amsterdam | |
| Comparisons | 1. 10‐ step evaluation scale (E10) 2. 5‐ step evaluation, tick box scale (E5‐B) 3. 5‐ step evaluation, circle answer scale (E5‐W) 4. 5‐ step satisfaction, tick box scale (S5‐B) 5. 5‐ step satisfaction, circle answer scale (S5‐W). | |
| Outcomes | Response period not specified | |
| Topic | Health: Sa tisfaction with hospital care | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Henley 1976.
| Methods | Random allocation: method not specified | |
| Data | Residents of Fort Worth, Texas | |
| Comparisons | 1. 1 by 4‐ inch slip of paper saying 'Please return by April 7th' stapled to the questionnaire 2. No deadline slip | |
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Civil issues | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hensley 1974.
| Methods | Random allocation: alternation | |
| Data | Members of the National Forensic League | |
| Comparisons | 1. Outer‐envelope (OE) commemorative Inner‐envelope (IE) commemorative 2. OE commemorative; IE regular 3. OE commemorative; IE metered 4. OE regular; IE commemorative 5. OE regular; IE regular 6. OE regular; IE metered 7. OE metered; IE commemorative 8. OE metered; IE regular 9. OE metered; IE metered | |
| Outcomes | Response period not specified | |
| Topic | Non‐health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Hewett 1974.
| Methods | Random allocation: coin toss | |
| Data | Individuals listed in a telephone directory | |
| Comparisons | 1. Hand‐stamped outgoing envelope; Hand‐stamped return envelope 2. Hand‐stamped outgoing envelope; First class postal permit business reply envelope | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Hoffman 1998.
| Methods | Random allocation: using terminal digit of study number or house number | |
| Data | Individuals who had previously participated in a campaign to collect blood for a specimen bank | |
| Comparisons | Study 1:
1. Short questionnaire
2. Long questionnaire Study 2: 1. No incentive 2. Newspaper article 3. Pencil 4. Pencil and newspaper article Study 3: 1. Postcard reminder 2. Second questionnaire and letter. |
|
| Outcomes | — | |
| Topic | Health: Family history of Cancer, reproductive history, medical and Vitamin use, history of medical conditions and surgery | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hopkins 1988.
| Methods | Random allocation: method not specified | |
| Data | Professional school and public librarians | |
| Comparisons | 1. $1 incentive
2. No incentive Non‐responders followed‐up after 1 month |
|
| Outcomes | — | |
| Topic | Non‐health: Attitudes and practices having a book in Spanish in the library | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hornik 1981.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in a telephone directory (Chicago, US) | |
| Comparisons | 1. Given time cue of 20 mins 2. Given time cue of 40 mins 3. Not given time cue | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Attitudes to TV advertising | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hornik 1982.
| Methods | Random allocation: method not specified. | |
| Data | Individuals listed in a telephone directory (Chicago, US) | |
| Comparisons | 1. Ingratiation appeal made in Pre‐notification telephone call (IA) ‐ Male telephone pre‐notified to Male respondent (M/M) 2. IA ‐ M/F 3. IA ‐ F/M 4. IA ‐ F/F 5. Polite imperative (PI) ‐ M/M 6. PI ‐ M/F 7. PI ‐ F/M 8. PI ‐ F/F 9. Rhetorical question (RQ) ‐ M/M 10. RQ ‐ M/F 11. RQ ‐ F/M 12. RQ ‐ F/F 13. Statement (S) ‐ M/M 14. S ‐ M/F 15. S ‐ F/M 16. S ‐ F/F 17. No pre‐notification. | |
| Outcomes | — | |
| Topic | Non‐health: People's attitudes to television and advertising | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Horowitz 1974.
| Methods | Random allocation: method not specified | |
| Data | Faculty members of the University of Maryland (US) | |
| Comparisons | 1. Status of researcher 'professor' (P); Ink Signature (I); Reproduction photocopied (R‐P) 2. Graduate Student (GS); I; R‐P 3. P; Non‐Ink (N‐I); R‐P 4. GS; N‐I; R‐P 5. P; I; Reproduction mimeographed (R‐M) 6. GS; I; R‐M 7. P; N‐I; R‐M 8. GS; N‐I; R‐M 9. P; I; R‐T 10. GS; I; R‐T | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: College professors Questionnaire | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Houston 1975.
| Methods | Random allocation: method not specified | |
| Data | New car buyers in Scott County, Iowa (US) | |
| Comparisons | 1. Personalised letter and questionnaire; Ball‐point pen incentive 2. Personalised letter and questionnaire; No incentive 3. Non‐personalised; Ball‐point pen incentive 4. Non‐personalised; No incentive | |
| Outcomes | — | |
| Topic | Non‐health: Sources of information used by the respondent in purchasing their new car | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Houston 1977.
| Methods | Random allocation: method not specified | |
| Data | Households listed in a telephone directory (Madison) | |
| Comparisons | 1. University Sponsor; Social Utility Appeal 2. Commercial Sponsor, Social Utility Appeal 3. University Sponsor, Help the Sponsor Appeal 4. Commercial Sponsor, Help the Sponsor Appeal 5. University Sponsor, Egoistic Appeal 6. Commercial Sponsor, Egoistic Appeal 7. University Sponsor, Combined Appeal 8. Commercial Sponsor, Combined Appeal | |
| Outcomes | Response within 1 month | |
| Topic | Non‐health: Tap consumer images and behaviour with respect to 5 Madison‐area shopping | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hubbard 1988a.
| Methods | Random allocation: method not specified | |
| Data | Residents of a major Midwestern metropolitan area | |
| Comparisons | 1. No incentive 2. Promise of $1 donation to charity of respondent's choice 3. 25 cents cash enclosed 4. $1 cash enclosed 5. Opportunity to win $200 cash prize | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Statis faction with banking and /financial services | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hubbard 1988b.
| Methods | Random allocation: method not specified | |
| Data | Residents of a major Midwestern metropolitan area | |
| Comparisons | 1. Control 2. Pre‐paid 25 cent incentive 3. Pre‐paid $1 incentive 4. Opportunity to win cash prize of $50 5. Opportunity to win cash prize of $100 6. Opportunity to win cash prize of $150 7. Opportunity to win cash prize of $200 8. Opportunity to win cash prize of $50 | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Satisfaction with banking and financial services | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Huck 1974.
| Methods | Random allocation: method not specified | |
| Data | Students living in residence halls at the university of Tennessee | |
| Comparisons | 1. First mailing with 25 cents incentive 2. Second mailing (to non‐respondents) with 25 cents incentive 3. Third mailing (to non‐respondents) with 25 cents incentive 4. First, second and third mailings without 25 cents incentive | |
| Outcomes | Response within 2 weeks | |
| Topic | Non‐health: Rokeach Dogmatism scale | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Hyett 1977.
| Methods | Random allocation: method not specified | |
| Data | Residential telephone subscribers | |
| Comparisons | 1. Double‐sided questionnaire
2. Single‐sided questionnaire After 2 weeks all non‐responders received another questionnaire. 1 week later all those who still had not responded were followed up by telephone |
|
| Outcomes | — | |
| Topic | Non‐health: Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Iglesias 2000.
| Methods | Random allocation: alternation | |
| Data | Women aged 70 years and over | |
| Comparisons | 1. 4‐ page questionnaire 2. 5‐ page questionnaire 3. 7‐page questionnaire | |
| Outcomes | — | |
| Topic | Health: Clinical questionnaire, EuroEoL, SF‐12 | |
| Mode of Administration | Postal | |
| Notes | Age: Above 70 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Iglesias 2001.
| Methods | Random allocation: alternation | |
| Data | Women aged 70 years or over selected from 2 general practices in North Yorkshire | |
| Comparisons | 1. Questionnaire with an individual item format 2. Questionnaire with a stem & leaf format | |
| Outcomes | Response period not specified | |
| Topic | Health: SF12 | |
| Mode of Administration | Postal. | |
| Notes | Age: Above 70 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Jacobs 1986.
| Methods | Random allocation: method not specified | |
| Data | Public school teachers (Indiana, US) | |
| Comparisons | 1. Short questionnaire; Optical scan form
2. Short questionnaire; Instructed to respond directly on questionnaire
3. Long questionnaire; Optical scan form
4. Long questionnaire; Instructed to respond directly on questionnaire Postcard follow up after 2 weeks |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes and opinions concerning discipline in the public schools | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jacoby 1990.
| Methods | Random allocation: method not specified | |
| Data | Individuals from 10 parliamentary areas (ISSMC questionnaires) Individuals from the electoral register (FPC questionnaires) |
|
| Comparisons | 1. Long questionnaire; Sent by ISSMC
2. Long questionnaire; Sent by FPC
3. Short questionnaire; Sent by ISSMC
4. Short questionnaire; Sent by FPC 1. Questionnaire included sensitive question; Sent by ISSMC 2. Questionnaire did not include sensitive question; Sent by ISSMC 3. Questionnaire included sensitive question; Sent by FPC 4. Questionnaire did not include sensitive question; Sent by FPC |
|
| Outcomes | — | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
James 1990a.
| Methods | Random allocation: method not specified | |
| Data | Cable television subscribers (Fairfax County, Virginia, US) | |
| Comparisons | 1. No incentive
2. $0.25
3. $50
4. $1
5. $2 3 follow‐up reminders sent without further monetary incentive at 3 week intervals |
|
| Outcomes | — | |
| Topic | Non‐health: Personal information. | |
| Mode of Administration | Postal. | |
| Notes | Author contacted: On the third follow up , participants were randomised to receive the questionnaire by first class or certified mailing but no data given for results | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
James 1990b.
| Methods | Random allocation: method not specified | |
| Data | Cable television subscribers who had failed to respond to 2 previous follow up attempts | |
| Comparisons | 1. Reminder by certified mail 2. Reminder by first class mail | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Personal information | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
James 1992.
| Methods | Random allocation: method not specified | |
| Data | Members of a national trade association of owners of construction subcontracting companies who were not currently enrolled in the association's health insurance programme | |
| Comparisons | 1. No incentive
2. $1 cash
3. $5 cash
4. $5 cheque
5. $10 cheque
6. $20 cheque
7. $40 cheque
8. Promise of $50 1‐page questionnaire, cover letter and business reply envelope. Reminders sent to non respondents at 3‐ week intervals |
|
| Outcomes | — | |
| Topic | Health: Health insurance | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jamtvedt 2008.
| Methods | Random allocation: block randomisation by computer generated table | |
| Data | Norwegian Physiotherapists from private practice | |
| Comparisons | 1. Dark chocolate 2. Control Group |
|
| Outcomes | Response period within 9 months | |
| Topic | Health: Treatment provided to 1 patient with osteoarthritis of knee through 12 treatment sessions | |
| Mode of Administration | Postal | |
| Notes | Randomisation was generated by Doris Tove Kristoffersen, who is not involved with any other aspect of the trial | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Jenkinson 2003.
| Methods | Random allocation: method not specified | |
| Data | Recently discharged patients from 2 English inner city NHS Trusts | |
| Comparisons | 1. 4‐page questionnaire 2. 12‐page questionnaire |
|
| Outcomes | Response period not specified | |
| Topic | Health: Picker Patient Experience Questionnaire | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jensen 1994.
| Methods | Random allocation: method not specified | |
| Data | Female graduates from the doctoral program in education from a private west‐coast university (US) | |
| Comparisons | 1. Open‐ended questions first; Closed questions next; Demographic questions last
2. Open; Demographic; Closed
3. Closed; Open; Demographic
4. Closed; Demographic; Open
5. Demographic; Open; Closed
6. Demographic; Closed; Open Reminders sent at 6 and 12 weeks. Some graduates were living out of the country at the time of the study. They were sent postal vouchers and an envelope instead of a stamped envelope on the initial mailing and first follow up. On the second follow up, US citizens received a telephone call while overseas received another postal mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Graduate school experiences | |
| Mode of Administration | Postal | |
| Notes | Age: 31‐65; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jepson 2005a.
| Methods | Random allocation: using random number generated in Excel | |
| Data | US Primary care physician members of the American Medical Association | |
| Comparisons | 1. Word count ‐ 849 2. Word count ‐ 1145 3. Word count ‐ 1163 4. Word count ‐ 1164 5. Word count ‐ 1215 6. Word count ‐ 1216 7. Word count ‐ 1234 8. Word count ‐1423 9. Word count ‐ 1424 10. Word count ‐ 1447 11. Word count ‐ 1449 12. Word count ‐ 1461 13. Word count ‐ 1462 14. Word count ‐ 1494 15. Word count ‐ 1496 16. Word count ‐ 1519 17. Word count ‐ 1520 18. Word count ‐ 1560 19. Word count ‐ 1561 20. Word count ‐ 1703 21. Word count ‐ 1706 22. Word count ‐ 1737 23. Word count ‐ 1744 24. Word count ‐ 1756 25. Word count ‐ 1776 26. Word count ‐ 1785 27. Word count ‐ 1788 28. Word count ‐ 1807 29. Word count ‐ 1855 30. Word count ‐ 1867 |
|
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes towards cost quality trade‐offs in clinical practice | |
| Mode of Administration | Postal | |
| Notes | Short length: From word count 849 ‐ 1234; Long length: From word count 1423 ‐ 1867; Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Jepson 2005b.
| Methods | Random allocation: using random number generated in Excel | |
| Data | US Primary care physician members of the American Medical Association | |
| Comparisons | 1. Word count ‐ 564 2. Word count ‐ 574 3. Word count ‐ 649 4. Word count ‐ 703 5. Word count ‐ 711 6. Word count ‐ 715 7. Word count ‐ 719 8. Word count ‐730 9. Word count ‐ 749 10. Word count ‐ 753 11. Word count ‐ 754 12. Word count ‐ 762 13. Word count ‐ 782 14. Word count ‐ 849 15. Word count ‐ 905 16. Word count ‐ 988 |
|
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes towards cost quality trade‐offs in clinical practice | |
| Mode of Administration | Postal | |
| Notes | Short length: From word count 564 to 730; Long length: From word count 749 to 905; Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Jobber 1983.
| Methods | Random allocation: method not specified | |
| Data | Textile companies listed in the Kompass‐Directory of UK Companies and 'Times Top 500' | |
| Comparisons | 1. Prior letter; White questionnaire 2. Prior letter; Blue questionnaire 3. No prior letter; White questionnaire 4. No prior letter; Blue questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Information about the marketing strategies employed by the company | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jobber 1985.
| Methods | Random allocation: method not specified | |
| Data | Senior marketing executives | |
| Comparisons | 1. Cover letter contained offer of a free copy of results as the final paragraph of the body of the letter 2. Same cover letter but offer made in typed postscript 3. Same cover letter but offer made in hand‐written postscript 4. Cover letter with no offer | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Explore the design and extent of implementation of marketing information system | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jobber 1988.
| Methods | Random allocation: method not specified | |
| Data | Building society chief executives | |
| Comparisons | 1. 20 pence incentive; No booklet 2. 20 pence incentive; Booklet explaining survey included 3. No incentive; No booklet 4. No incentive; Booklet explaining survey included | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Ascertain management practices, and contextual and structural characteristics of societies | |
| Mode of Administration | Postal | |
| Notes | Number of subjects allocated to each intervention group ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jobber 1989.
| Methods | Random allocation: method not specified | |
| Data | Industrial goods companies | |
| Comparisons | 1. Short questionnaire;
1‐sided printing
2. Short questionnaire;
2‐sided printing
3. Long questionnaire;
1‐sided printing
4. Long questionnaire; 2‐sided printing The long questionnaire comprised 2 different versions of a short questionnaire. The 2 versions were allocated randomly between treatments. |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Selling approach and orientations used by the sample firms, evaluate the sale persons, size of firm, industry category, number of sales persons employed | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jobber D 1985.
| Methods | Random allocation: systematic random sampling | |
| Data | Quality control managers of textile companies randomly selected from a directory of UK companies | |
| Comparisons | 1. No pre‐notification 2. Telephone pre‐notification | |
| Outcomes | Response prior to second wave of the experiment | |
| Topic | Non‐health: Quality management systems used by UK textile companies. | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Johansson 1997a.
| Methods | Random allocation: method not specified | |
| Data | Norwegian citizens aged 16‐79 years | |
| Comparisons | 1. No reward offered
2. Reward offered 1 reminder sent after 4 weeks |
|
| Outcomes | Response period not specified | |
| Topic | Health: Quantitative Food Frequency Questionnaire (QFFQ) | |
| Mode of Administration | Postal | |
| Notes | Mean age: 42‐47 | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Johansson 1997b.
| Methods | Random allocation: method not specified | |
| Data | Norwegian citizens aged 16‐79 years | |
| Comparisons | 1. No reward offered
2. Reward offered 1 reminder sent after 4 weeks |
|
| Outcomes | Response period not specified | |
| Topic | Health: Quantitative Food Frequency Questionnaire (QFFQ) | |
| Mode of Administration | Postal | |
| Notes | Mean age: 42‐47 | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Johansson 1997c.
| Methods | Random allocation: method not specified | |
| Data | Norwegian citizens aged 16‐79 years who had not responded to a questionnaire | |
| Comparisons | 1. Follow up by telephone 2. Follow up by post | |
| Outcomes | Response period not specified | |
| Topic | Health: Quantitative Food Frequency Questionnaire (QFFQ) | |
| Mode of Administration | Postal | |
| Notes | Mean age: 42‐47 | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
John 1994.
| Methods | Random allocation: method not specified | |
| Data | Cosmetologists aged 22 to 36 years | |
| Comparisons | 1. $1 incentive in first mailing
2. $1 incentive in second mailing
3. No incentive 2‐ page questionnaire, cover letter, survey fact sheet and stamped addressed envelope. Reminder postcard sent 1 week after first mailing |
|
| Outcomes | Response period not specified | |
| Topic | Health: Screening questions ‐ recent health problems, reproductive history; outcome of the most recent pregnancy | |
| Mode of Administration | Postal | |
| Notes | Age: 22‐36; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Joinson 2005a.
| Methods | Random allocation: using random number generated in Excel | |
| Data | Students at the Open University, UK | |
| Comparisons | 1. Salutation ‐ 'Dear Student' 2. Salutation ‐ 'Dear Open University Student' 3. Salutation ‐ 'Dear Forename' (e.g. Dear John) 4. Salutation ‐ 'Dear Forename Surname' (e.g. Dear John Doe) |
|
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Volunteering to become a member of a survey panel (PRESTO) | |
| Mode of Administration | Electronic: E‐mail | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Joinson 2005b.
| Methods | Random allocation: using random number generated in Excel | |
| Data | Students at the Open University, UK | |
| Comparisons | 1. Salutation ‐ 'Dear Student' 2. Salutation ‐ 'Dear Open University Student' 3. Salutation ‐ 'Dear Forename' (e.g. Dear John) 4. Salutation ‐ 'Dear Forename Surname' (e.g. Dear John Doe) |
|
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Inviting the existing panel members to exit the panel | |
| Mode of Administration | Electronic: E‐mail | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Joinson 2005c.
| Methods | Random allocation: using random number generated in Excel | |
| Data | Students at the Open University, UK | |
| Comparisons | 1. Salutation ‐ 'Dear Student' 2. Salutation ‐ 'Dear Forename' ( e.g. Dear John) 3. Salutation ‐ 'Dear Forename Surname' (e.g. Dear John Doe) 4. High Power ‐ "From Professor (name), Pro‐Vice chancellor, (Strategy, planning and partnerships), The OU 5. Neutral Power ‐ "From (name), (Strategy, planning and partnerships), The OU |
|
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Inviting the panel members to complete the survey | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Joinson 2007a.
| Methods | Random allocation: using random number generated in Excel | |
| Data | Members of an online student panel at the Open University, UK | |
| Comparisons | 1. High Power ‐ "From Professor (name), Pro‐Vice chancellor, (Strategy, planning and partnerships), The OU 2. Neutral Power ‐ "From (name), (Strategy, planning and partnerships), The OU 3. Salutation ‐ 'Dear Forename' ( e.g. Dear John) 4. Salutation ‐ 'Dear Presto panel member' |
|
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Socio‐economic status | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author; Mean age: 41.8 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Joinson 2007b.
| Methods | Random allocation: using random number generated in Excel | |
| Data | Members of an online student panel at the Open University, UK | |
| Comparisons | 1. Personalised URL (Unique URL with identifier encoded in the link) 2. Authentication required (URL requires log‐on to access the survey) |
|
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Part‐time student costs and fees | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author; Mean age: 43.6 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Jones 1978.
| Methods | Random allocation: method not specified | |
| Data | Individuals who had planned group conventions and/or meetings | |
| Comparisons | 1. Science appeal (SA); Commemorative stamp (CS); J&L sponsor (J&L) 2. SA; CS; University sponsor (US) 3. SA; CS; Government sponsor (GS) 4. SA; Regular stamp (RS); J&L 5. SA; RS; US 6. SA; RS; GS 7. SA; Business reply envelope (BR); J&L 8. SA; BR; US 9. SA; BR; GS 10. User appeal (UA); CS; J&L 11. UA; CS; US 12. UA; CS; GS 13. UA; RS; J&L 14. UA; RS; US 15. UA; RS; GS 16. UA; BR; J&L 17. UA; BR; US 18. UA; BR; GS 19. Resort park appeal (RA); CS; J&L 20. RA; CS; US 21. RA; CS; GS 22. RA; RS; J&L 23. RA; RS; US 24. RA; RS; GS 25. RA; BR; J&L 26. RA; BR; US 27. RA; BR; GA | |
| Outcomes | Response within 6 weeks | |
| Topic | Non‐health: Characteristics of the group, respondent attitudes towards meeting facilities, demographic factors | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Jones 2000.
| Methods | Random allocation: method not specified | |
| Data | Adult patients admitted for treatment between 14/09/98 and12/12/98 | |
| Comparisons | 1. No incentive 2. $2 3. $5 4. SF‐36 5. SF‐12 6. MH‐5 7. MH‐1 |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health status survey | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Junghans 2005.
| Methods | Random allocation: using minimisation software | |
| Data | 2 general practices in England | |
| Comparisons | 1. Opt‐in (asked to actively signal willingness to participate in research) 2. Opt‐out (contacted repeatedly unless they signalled unwillingness to participate) |
|
| Outcomes | Response period within 2 weeks | |
| Topic | Health: Patients with angina | |
| Mode of Administration | Postal | |
| Notes | The identity of the trial was kept in a sealed envelope and was known only to the research assistant | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Kahle 1978.
| Methods | Random allocation: method not specified | |
| Data | Psychiatrists and clinical psychologists | |
| Comparisons | Experiment 1:
1. Dillman's
3‐wave mailing design
2. As (1) except first
2 waves received non‐profit bulk rate permit number printed where stamp had been
3. As (2) except pre‐printed labels used to address envelopes rather than addresses typed individually on envelopes Experiment 2: As experiment 1 but in final wave questionnaire sent by: 1. Certified mail 2. First class mail |
|
| Outcomes | Response period not specified | |
| Topic | Health: Involuntary civil commitments | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kalafatis 1995.
| Methods | Random allocation: using random number generation | |
| Data | Danish participants in a non‐price‐based promotion that utilised an American sporting theme | |
| Comparisons | 1. No incentives 2. Unconditional 5% value of coupon 3. Unconditional 10% value of coupon 4. Unconditional 15% value of coupon 5. Conditional 5% value of coupon 6. Conditional 10% value of coupon 7. Conditional 15% value of coupon 8. Free gift 9. No free gift. |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Sports ‐ promotional offers, viewing patterns of sports programmes, shopping habits of sports goods and perceptions of different sports | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kalantar 1999.
| Methods | Random allocation: computerised random number generation | |
| Data | Residents of Western S ydney, Australia | |
| Comparisons | 1. Long questionnaire (7 pages) 2. Short questionnaire (1 page) 3. Scratch lottery worth $1 to win up to $2500 4. No lottery |
|
| Outcomes | Response period not specified | |
| Topic | Health: Bowel function and faecal incontinence | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Kaplan 1970a.
| Methods | Random allocation: using alternation | |
| Data | Residents of Boston and Brockton, Massachusetts, USA | |
| Comparisons | 1. Long questionnaire 2. Short questionnaire 3. Impersonal letter (no inside address and the salutation is 'Dear Madam') 4. Personal letter (with complete address and the salutation is 'Dear Mrs. name) 5. Stamped return envelope 6. Franked return envelope 7. Non‐specific signer 8. Jewish signer 9. Irish signer |
|
| Outcomes | Response period not specified | |
| Topic | Health: Reproductive history and the use of oral contraceptives | |
| Mode of Administration | Postal | |
| Notes | Age: 20‐70 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Kaplan 1970b.
| Methods | Random allocation: using alternation | |
| Data | Residents of Boston and Brockton, Massachusetts, USA | |
| Comparisons | 1. Irish signer 2. Irish, Professor signer 3. Non‐specific signer |
|
| Outcomes | Response period not specified | |
| Topic | Health: Reproductive history and the use of oral contraceptives | |
| Mode of Administration | Postal | |
| Notes | Age: 20‐70 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Kaplowitz 2004.
| Methods | Random allocation: using alternation | |
| Data | Residential and agricultural landowners in the Sycamore creek watershed, USA | |
| Comparisons | 1. Survey instrument ‐ Colour 2. Survey instrument ‐ Black and White |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Homeowner preferences for watershed management practices | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Kasprzyk 2001.
| Methods | Random allocation: method not specified | |
| Data | Sample of the general internists listed on the American Medical Association files who spend time on direct patient care, deal with STD diagnosis and have a listed mailing address | |
| Comparisons | 1. First class mailing; No incentive 2. First class mailing; $15 cash 3. First class mailing; $25 cash 4. FedEx mailing; No incentive 5. FedEx mailing; $15 cash 6. FedEx mailing; $25 cash | |
| Outcomes | Response after final reminder mailing, 8 weeks after initial survey | |
| Topic | Health: Physician and practice characteristics, STD diagnosis. treatment and control practice, opinions about STD reporting requirements and partner notification | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kawash 1971.
| Methods | Random allocation: using table of random numbers | |
| Data | Faculty members of University of Illinois | |
| Comparisons | 1. Personal signature 2. Mimeographed facsimile |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes towards audiovisual instructional materials | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Keeter 2001.
| Methods | Random allocation: method not specified | |
| Data | Attorneys, clinical social workers, college and university faculty, staff and students, employees and employers in business organisations and a sample of physicians | |
| Comparisons | 1. White questionnaire 2. Pink questionnaire 3. Green questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Health: Purchase of major medical equipments Non‐health: Housing market, parking and ridesharing, workload, distribution of time, attitudes |
|
| Mode of Administration | Postal | |
| Notes | Results of 7 different studies all examining the same intervention over a 14‐ month period | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kenyon 2005.
| Methods | Random allocation: method not specified | |
| Data | Mothers of the MRC ORACLE Trial that evaluated the use of antibiotics to improve neonatal outcome after preterm labour/preterm rupture of the membrane | |
| Comparisons | 1. £5 voucher 2. No voucher |
|
| Outcomes | Response period not specified | |
| Topic | Health: Child's health and development | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Keown 1985a.
| Methods | Random allocation: method not specified | |
| Data | Japanese business executives | |
| Comparisons | 1. $1 incentive 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes towards business risk | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Keown 1985b.
| Methods | Random allocation: method not specified | |
| Data | Business executives (Hong Kong) | |
| Comparisons | 1. $1 incentive 2. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes towards business risk | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kephart 1958.
| Methods | Random allocation: method not specified | |
| Data | Women who had passed their Pennsylvania State Nursing Board exams | |
| Comparisons | 1. Regular stamp; No preview or follow up 2. Preview sent 1 week prior to questionnaire 3. Follow up (duplicate questionnaire, letter and return envelope) 4. Preview and follow up 5. Air mail stamp 6. Special delivery mail 7. Incentive of a penny 8. Incentive of a nickel 9. Incentive of a dime 10. Incentive of a quarter | |
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes towards nursing profession | |
| Mode of Administration | Postal | |
| Notes | Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kerin 1976.
| Methods | Random allocation: method not specified | |
| Data | Corporate presidents from 'Fortune 500' firms | |
| Comparisons | 1. Individual cover letter; Altruistic appeal; Stamp on return envelope 2. Individual; Altruistic; No stamp 3. individual; Egoistic appeal; Stamp 4. individual; Egoistic; No stamp 5. Form cover letter; Altruistic; Stamp 6. Form cover letter; Altruistic; No stamp 7. Form; Egoistic; Stamp 8. Form; Egoistic; No stamp | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Product recall practices | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kerin 1981.
| Methods | Random allocation: method not specified | |
| Data | Senior marketing executives | |
| Comparisons | 1. Offered results 2. Not offered results | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Interaction between sales and advertising functions in the design and execution of promotion strategy | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kernan 1971.
| Methods | Random allocation: method not specified | |
| Data | Residents of Cincinnati | |
| Comparisons | 1. Personalised address; First class 2. Personalised address; Bulk rate 3. Occupant address; First class 4. Occupant address; Bulk rate | |
| Outcomes | Response within 3 weeks | |
| Topic | Non‐health: Community's general interest in new sports stadium | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kindra 1985.
| Methods | Random allocation: method not specified | |
| Data | Households listed in a telephone directory (Montreal, Canada) | |
| Comparisons | 1. Pre‐contact; Lottery incentive 2. No pre‐contact; Lottery incentive 3. Pre‐contact; No lottery incentive 4. No pre‐contact; No lottery incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Elicit consumer response to product advertising | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
King 1978.
| Methods | Random allocation: systematic sampling procedure with random start | |
| Data | Registered bank holding companies | |
| Comparisons | 1. Cover letter most personalised 2. Cover letter least personalised | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Koloski 2001.
| Methods | Random allocation: random block procedure | |
| Data | People aged 18 years and above listed on the 1996 Local Government electoral role, Penrith, Australia | |
| Comparisons | 1. Short (28 page) questionnaire; Lottery card included 2. Short questionnaire; No lottery card 3. Long questionnaire (32 pages); Lottery card included 4. Long questionnaire; No lottery card | |
| Outcomes | Response after 8 phases of follow up | |
| Topic | Health: Questions on common health problems especially on stomach and bowel, Delusions Symptoms States Inventory, SF‐12 | |
| Mode of Administration | Postal | |
| Notes | Age: 41.9‐46.6 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Koo 1995.
| Methods | Random allocation: random function in Microsoft Excel programme | |
| Data | Girls recruited by volunteers from the Canadian Cancer Society | |
| Comparisons | 1. Real signature on cover letter 2. Printed signature | |
| Outcomes | Response within 105 days | |
| Topic | Health: Dietary and life style determinants of the onset of menarche | |
| Mode of Administration | Postal | |
| Notes | Allocation was not concealed; Age: 7.5‐14.9 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Koo 1996.
| Methods | Random allocation: method not specified | |
| Data | Girls recruited by volunteers from the Canadian Cancer Society who had not responded in a previous study | |
| Comparisons | 1. Regular reminder letter 2. Reminder letter with telephone reminder indicated 3. Reminder letter with telephone interview indicated | |
| Outcomes | Response within 16 days (prior to telephone interview) | |
| Topic | Health: Dietary and life style determinants of the onset of menarche | |
| Mode of Administration | Postal | |
| Notes | Age: 8.7‐16.2 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kropf 2005.
| Methods | Random allocation: method not specified | |
| Data | Members of the Health Maintenance Organizations (HMOs) in Maryland | |
| Comparisons | 1. $5 incentive 2. No incentive 3. Cover letter ‐ Norms of co‐operation (answering the survey would help many other people) 4. Cover letter ‐ Norms of self‐intrest (cooperation would help the survey respondent himself or herself). |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health care and other current issues | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kurth 1987.
| Methods | Random allocation: method not specified | |
| Data | Employees of the Maricopa Community Colleges with e‐mail accounts | |
| Comparisons | 1. Type‐written; Sensitive question 2. Type‐written; No sensitive question | |
| Outcomes | Response within 30 days | |
| Topic | Non‐health: Supervisory management | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kuskowska‐Wolk 1992.
| Methods | Random allocation: method not specified | |
| Data | Women aged 40‐70 years from 2 medium‐sized towns in Uppsala Health Care Region invited for mammography over the period 13 October 1986 to 20 March 1987 | |
| Comparisons | 1. Increasing order of food frequencies; No column on portion sizes; No extra page of questions 2. Decreasing order of food frequencies; No column on portion sizes; No extra page of questions 3. Increasing order of food frequencies; Column on portion sizes; No extra page of questions 4. Decreasing order of food frequencies; Column on portion sizes; No extra page of questions 5. Increasing order of food frequencies; No column on portion sizes; Extra page of questions 6. Decreasing order of food frequencies; No column on portion sizes; Extra page of questions 7. Increasing order of food frequencies; Column on portion sizes; Extra page of questions 8. Decreasing order of food frequencies; Column on portion sizes; Extra page of questions | |
| Outcomes | Response period not specified | |
| Topic | Health: Food Frequency Questionnaire | |
| Mode of Administration | Postal | |
| Notes | Age: 54.9‐55.6 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Kypri 2003.
| Methods | Random allocation: method not specified | |
| Data | Tertiary students at the University of Otago | |
| Comparisons | 1. Ball‐point pen worth $0.50 2. Pen + Cookie voucher worth $1 3. Pen + Lunch voucher worth $5 4. Pen + Lunch voucher worth $5 on completion of the survey. |
|
| Outcomes | Response period not specified | |
| Topic | Health: Alcohol use | |
| Mode of Administration | Electronic: Web survey | |
| Notes | Age: 16‐29 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
La Garce 1995.
| Methods | Random allocation: method not specified | |
| Data | Goodyear tyre and rubber dealers | |
| Comparisons | 1. Standard questionnaire printed in black and white 2. Standard questionnaire printed in blue and yellow 3. User‐friendly format questionnaire printed in black and white 4. User‐friendly format questionnaire printed in blue and yellow | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Industry | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Labarere 2000.
| Methods | Random allocation: method not specified | |
| Data | 400 people recently discharged from hospital | |
| Comparisons | 1. Postal questionnaire, no follow up 2. Postal questionnaire with follow up | |
| Outcomes | Response within 2 months | |
| Topic | Health: Patient Satisfaction | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Labrecque 1978.
| Methods | Random allocation: method not specified | |
| Data | Service customers of a marina | |
| Comparisons | 1. Owner's signature (OS); Personalised (P); Commemorative stamp (CS) 2. Service manager's signature (SMS); P; CS 3. OS; Not personalised (NP); CS 4. SMS; NP; CS 5. OS; P; No CS 6. SMS; P; No CS 7. OS; NP; No CS 8. SMS; NP; No CS | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Reaction of customers to the performance of its service department | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Lavelle 2008.
| Methods | Random allocation: using SPSS | |
| Data | Patients attending breast clinics in Greater Manchester between 1/10/2002 ‐ 31/7/2003 | |
| Comparisons | 1. First class stamp on addressed reply envelope 2. Pre‐paid addressed reply envelope |
|
| Outcomes | Response period not specified | |
| Topic | Health: Functional health status ‐ ELPHS ADL; Generic health status ‐ SF‐12; Health related quality of life ‐ EORTC QLQ‐C30 | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Leece 2006a.
| Methods | Random allocation: using alternation | |
| Data | Surgeon members of the Orthopaedic Trauma Association | |
| Comparisons | 1. Standard cover letter 2. Test cover letter (more personal) |
|
| Outcomes | Response period is 6 weeks | |
| Topic | Health: Preferences in the treatment of femoral neck fractures | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Leece 2006b.
| Methods | Random allocation: using alternation | |
| Data | Surgeon members of the Orthopaedic Trauma Association | |
| Comparisons | 1. Standard cover letter 2. Test cover letter (more personal) |
|
| Outcomes | Response period is 6 weeks | |
| Topic | Health: Preferences in the treatment of femoral neck fractures | |
| Mode of Administration | Electronic: E‐mail | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Leigh Brown 1997.
| Methods | Random allocation: method not specified | |
| Data | Patients who had already responded a questionnaire about hospital attendance | |
| Comparisons | 1. Aware of monthly prize draw offering £25 gift voucher 2. Unaware of monthly prize draw offering £25 gift voucher | |
| Outcomes | Response period not specified | |
| Topic | Health: Health status, satisfaction with orthopaedic referral | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Leung 2002.
| Methods | Random allocation: computerised random number generation | |
| Data | Physicians randomly selected from the full and limited registration lists of the Hong Kong medical council | |
| Comparisons | 1. No incentive 2. $10 cash 3. $20 cash 4. $40 cash 5. Entry into $1000 lottery 6. Entry into $2000 lottery 7. Entry into $4000 lottery | |
| Outcomes | Response within 30 days | |
| Topic | Health: Nature of practice, remuneration, clinical and administrative task | |
| Mode of Administration | Postal | |
| Notes | Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Leung 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | Physicians randomly selected from the full and limited registration lists of the Hong Kong medical council | |
| Comparisons | 1. Prepayment HK$ 20 2. Post‐payment HK$ 20 |
|
| Outcomes | Response within 60 days | |
| Topic | Health: Computerisation of clinical and administrative tasks | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Linsky 1965.
| Methods | Random allocation: method not specified | |
| Data | Nurses | |
| Comparisons | 1. Characteristics of cover letter: personalised (P); social utility appeal (SU); explanation of place and importance of respondent in study (RP); an appeal to help researchers of study (HR) 2. Not P; SU; RP; HR 3. P; Not SU; RP; HR 4. Not P; Not SU; RP; HR 5. P; SU; Not RP; HR 6. Not P; SU; Not RP; HR 7. P; SU; RP; Not HR 8. Not P; SU; RP; Not HR 9. P; Not SU; Not RP; HR 10. Not P; Not SU; Not RP; HR 11. P; Not SU; RP; Not HR 12. Not P; Not SU; RP; Not HR 13. P; SU; Not RP; Not HR 14. Not P; SU, Not RP; Not HR 15. P; Not SU; Not RP; Not HR 16. Not P; Not SU; Not RP; Not HR | |
| Outcomes | Response within 3 weeks | |
| Topic | Health: Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Little 1990.
| Methods | Random allocation: using alternation | |
| Data | Respondents to a national magazine clip ad promotion | |
| Comparisons | 1. 25‐cent 2. Pan‐scrapper 3. Control |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perceptions of the product and follow‐up service to competing products | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
London 1990a.
| Methods | Random allocation: method not specified | |
| Data | Electronics design engineers | |
| Comparisons | 1. Standard cover letter 2. As (1) but also told would be entered into a prize draw for 3 calculators if responded 3. As (2) but also told that all respondents would receive a special gift from the sponsor | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Potential customers needs, firm usage, sources of transformers and inductors | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
London 1990b.
| Methods | Random allocation: method not specified | |
| Data | Electronics design engineers | |
| Comparisons | 1. No incentive 2. $1 incentive | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Potential customers needs, firm usage, sources of transformers and inductors | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Lorenzi 1988.
| Methods | Random allocation: methods not specified | |
| Data | Business executives, state legislators, and director of chambers of commerce from the Midwestern United States | |
| Comparisons | 1. Unconditional $1 payoff 2. Conditional $2 payoff 3. Lottery to win $50, $30, or $20 4. No incentives |
|
| Outcomes | Response within 14 days | |
| Topic | Non‐health: Finance ‐ Financial investment scenario, behavioural self‐description measure of propensity for risk in personal and business investments | |
| Mode of Administration | Postal | |
| Notes | Mean age: 49.7 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Lund 1998.
| Methods | Random allocation: method not specified | |
| Data | Norwegian women aged 34‐49 years | |
| Comparisons | 1. Questionnaire entitled 'Women Lifestyle & Health'; 4 pages 2. Questionnaire entitled "Women & Cancer"; 2 pages 3. Questionnaire entitled "Women & Cancer"; 4 pages 4. Questionnaire entitled "Women & Cancer"; 6 pages 5. Questionnaire entitled "Oral Contraceptives & Cancer"; 2 pages | |
| Outcomes | Response period not specified | |
| Topic | Health: Diet, sunbathing habits, occupational exposure, pharmaceutical drugs | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Maheux 1989a.
| Methods | Random allocation: method not specified | |
| Data | Physicians who had failed to respond to a previous questionnaire (Quebec, UK) | |
| Comparisons | 1. Follow‐up letter with hand‐written postscript 2. Follow‐up letter with no postscript | |
| Outcomes | Response within 6 months | |
| Topic | Health: Support for patient care issues | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Maheux 1989b.
| Methods | Random allocation: method not specified | |
| Data | Physicians who had failed to respond to 2 mailings of a questionnaire (Quebec, UK) | |
| Comparisons | 1. Personalised mail out package 2. Non‐personalised mail out package | |
| Outcomes | Response within 6 months | |
| Topic | Health: Support for patient care issues | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mallen 2008.
| Methods | Random allocation: computer generated | |
| Data | Patients aged 50 and over from the Central Cheshire general practices who consulted their GP for non‐inflammatory musculoskeletal pain between September 2006 – April 2007 | |
| Comparisons | 1. Small font size ‐ Arial 12 2. Large font size ‐ Arial 16 3. Thin paper ‐ 80g 4. Thick paper ‐ 100g |
|
| Outcomes | Response period not specified | |
| Topic | Health: Prognosis of older people with joint pain in general practice | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Mann 2005.
| Methods | Random allocation: method not specified | |
| Data | Registered voters in Maryland, New York, and Pennsylvania | |
| Comparisons | 1. Advance letter 2. No advance letter |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Voting behaviour | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Marcus 2007.
| Methods | Random allocation: Using random number generation in SPSS | |
| Data | Owners of personal website | |
| Comparisons | 1. High topic salience ‐ Motives and personality of personal website owners 2. Low topic salience ‐ Psychological aspects of Internet usage 3. Long survey ‐ 359 items, 30‐60 minutes for completion 4. Short survey ‐ 91 items, 10‐20 minutes for completion 5. Lottery to win 2 Internet book store vouchers of 25 euro each 6. No lottery 7. Personalised feedback of the results (individual profile of the results) 8. Generalised (study results) or no Feedback |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Internet competence | |
| Mode of Administration | Electronic: Web survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Marrett 1992.
| Methods | Random allocation: method not specified | |
| Data | Residents with histologically confirmed renal cell carcinoma (Ontario, US) | |
| Comparisons | 1. Lottery ticket incentive 2. No incentive | |
| Outcomes | — | |
| Topic | Health: History of urinary tract infection, use of analgesic and diuretic medication, demographics | |
| Mode of Administration | Postal | |
| Notes | Allocation was not concealed from the person sending out the letters; Age: 25‐69 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Marsh 1999.
| Methods | Random allocation: alternation | |
| Data | Parents of children aged 3‐12 months from general practices involved in a cluster randomised trial in Nottingham, UK who had responded to a previous questionnaire | |
| Comparisons | 1. Promise of a £2 voucher for a local children's store on return of the questionnaire (Postal) 2. No incentive (Postal) | |
| Outcomes | Response period not specified | |
| Topic | Health: Near miss and minor injuries | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Martin 1970.
| Methods | Random allocation: method not specified. | |
| Data | Individuals listed in a telephone directory (Washington, US) | |
| Comparisons | 1. Personalised letter (PL); Appeal to importance (AI); Commemorative Stamp (CS); Easy questionnaire (EQ) first 2. PL; AI; CS; EQ not first 3. PL; AI; Business reply frank (BRF) instead of CS 4. PL; AI; BRF; EQ not first 5. PL; No AI; CS; EQ first 6. PL; No AI; CS; EQ not first 7. PL; No AI; BRF; EQ first 8. PL; No AI; BRF; EQ not first 9. Letter not personalised (NPL); AI; CS; EQ first 10. NPL; AI; CS; EQ not first 11. NPL; AI; BRF; EQ first 12. NPL; AI; BRF; EQ not first 13. NPL; No AI; CS; EQ first 14. NPL; No AI; CS; EQ not first 15. NPL; No AI; BRF; EQ first 16. NPL; No AI; BRF; EQ not first | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Public and judicial attitudes toward various aspects of the legal machinery | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Martin 1989.
| Methods | Random allocation: method not specified | |
| Data | University students | |
| Comparisons | 1. Pre‐notification (PN); Follow up (FU); Personalised (PS); Stamped reply envelope (SRE) 2. PN; No FU; PS; SRE 3. PN; FU; No PS; SRE 4. PN; No FU; No PS; SRE 5. PN; FU; PS; Business reply envelope (BRE) 6. PN; No FU; PS; BRE 7. PN; FU; No PS; BRE 8. PN; No FU; No PS; BRE 9. No PN; FU; PS; SRE 10. No PN; No FU; PS; SRE 11. No PN; FU; No PS; SRE 12. No PN; No FU; No PS; SRE 13. No PN; FU; PS; BRE 14. No PN; No FU; PS; BRE 15. No PN; FU; No PS; BRE 16. No PN; No FU; No PS; BRE | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Information on the perceived attributes of the university | |
| Mode of Administration | Postal | |
| Notes | Mean age: 30 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Martin 1994.
| Methods | Random allocation: method not specified | |
| Data | Participants of a large international amateur bowling tournament | |
| Comparisons | 1. High‐interest questionnaire 2. Low‐interest questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Interpersonal relationships with other customers in service environment | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Martinson 2000.
| Methods | Random allocation: method not specified | |
| Data | Adolescents aged 14‐17 years in the Minneapolis/St Paul metropolitan area | |
| Comparisons | 1. $2 included with questionnaire 2. $15 promised on completion and return of questionnaire 3. Promise of entry into 10 drawings for 10 $200 cash prizes on completion and return of questionnaire 4. No incentive | |
| Outcomes | — | |
| Topic | Health: Attitudes towards smoking, behavioural health related items | |
| Mode of Administration | Postal | |
| Notes | Reminder and second questionnaire sent to non‐responders 1 week and 3 weeks after initial mailing, respectively; Age: 14‐17 years; Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mason 1961.
| Methods | Random allocation: alternation | |
| Data | Teachers | |
| Comparisons | 1. Long form; Name and address on form 2. Long form; Code number on form 3. Short form; Name and address on form 4. Short form; Code number on form | |
| Outcomes | — | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Matteson 1974.
| Methods | Random allocation: method not specified | |
| Data | Members of a national organisation | |
| Comparisons | 1. Semi‐personalised letter; White questionnaire 2. Semi‐personalised letter; Pink questionnaire 3. Form letter; White questionnaire 4. Form letter; Pink questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Significant contribution of literature in their field | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McColl 2003a.
| Methods | Random allocation: method not specified | |
| Data | Adults with angina form 62 family practices in Northeast England | |
| Comparisons | 1. Version 1: Condition‐specific questionnaires (Seattle Angina Questionnaire) first, followed by generic questionnaires (SF‐36 & EQ‐5D) 2. Version 2: Generic questionnaires first, followed by condition‐specific questionnaires |
|
| Outcomes | Response period not specified | |
| Topic | Health: Patient‐based outcome measures | |
| Mode of Administration | Postal | |
| Notes | Reminder and second questionnaire sent to non‐responders 3 weeks and 6 weeks after initial mailing, respectively; Mean age: 69.1 years; mainly male | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McColl 2003b.
| Methods | Random allocation: method not specified | |
| Data | Adults with asthma from 62 family practices in Northeast England | |
| Comparisons | 1. Version 1: Condition‐specific questionnaires (Newcastle Asthma Symptoms Questionnaire & Asthma Quality of Life Questionnaire) first, followed by generic questionnaires (SF‐36 & EQ‐5D) 2. Version 2: Generic questionnaires first, followed by condition‐specific questionnaires |
|
| Outcomes | Response period not specified | |
| Topic | Health: Patient‐based outcome measures | |
| Mode of Administration | Postal | |
| Notes | Reminder and second questionnaire sent to non‐responders 3 weeks and 6 weeks after initial mailing, respectively; Mean age: 48.6 years; mainly female | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McConochie 1985.
| Methods | Random allocation: method not specified | |
| Data | Males aged 18‐34 | |
| Comparisons | 1. 50 cents incentive 2. $2 incentive 3. $5 incentive | |
| Outcomes | Response within 1 week | |
| Topic | Non‐health: Measurement of radio listening | |
| Mode of Administration | Postal | |
| Notes | Age: 18‐34 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McCoy 2007.
| Methods | Random allocation: using alternation | |
| Data | Institute of Public Relations (IPR) members in Northern Ireland | |
| Comparisons | 1. Hand written address 2. Computer‐printed address 3. Brown envelope 4. White envelope |
|
| Outcomes | Deadline for return provided | |
| Topic | Non‐health: Practices and attitudes towards public relations evaluation | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
McDaniel 1980.
| Methods | Random allocation: using alternation | |
| Data | Major‐appliances purchasers | |
| Comparisons | 1. 25‐cent incentive 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Product warranty questionnaire | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McDaniel 1981.
| Methods | Random allocation: using alternation | |
| Data | Major‐appliances purchasers in Midwestern US | |
| Comparisons | 1. Anonymous (no name requested and no name given) 2. Non‐anonymous (name requested and given at the beginning of questionnaire) |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Major appliances warranties and warranty performance | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McKee 1992.
| Methods | Random allocation: method not specified | |
| Data | Members of a national non‐profit professional organisation | |
| Comparisons | 1. Coded
2. Not coded In coded group, only non‐respondents received follow up . In non‐coded group, all received follow up |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Programme of the organisation | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McKenzie‐McHarg 2005.
| Methods | Random allocation: computerised random number generation | |
| Data | Members and fellows of the Royal College of Obstetricians and Gynaecologists in the UK | |
| Comparisons | 1. Hand‐written signature in the cover letter 2. Scanned and printed signature in the cover letter |
|
| Outcomes | Response period not specified | |
| Topic | Health: Surgical techniques used in caesarean section operation in the UK | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McKillip 1984.
| Methods | Random allocation: method not specified | |
| Data | Underclass men of a large rural Midwestern university (US) | |
| Comparisons | 1. Utility cover letter appeal 2. Value expression appeal 3. Knowledge appeal | |
| Outcomes | Response period not specified | |
| Topic | Health: Evaluation activities for an alcohol education project | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McLaren 2000a.
| Methods | Random allocation: method not specified | |
| Data | 700 Victorian general practitioners selected from a database held by Australasian Medical Publishing Company | |
| Comparisons | 1. Telephone pre‐notification 2. Postcard pre‐notification | |
| Outcomes | Response within 8 weeks | |
| Topic | Health: Management of early pregnancy, bleeding and miscarriage, referral, diagnostic methods | |
| Mode of Administration | Postal | |
| Notes | Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
McLaren 2000b.
| Methods | Random allocation: method not specified | |
| Data | 700 Victorian general practitioners selected from a database held by Australasian Medical Publishing Company | |
| Comparisons | 1. Promise of entry into a prize draw for a holiday on response 2. No incentive | |
| Outcomes | Response within 8 weeks | |
| Topic | Health: Management of early pregnancy, bleeding and miscarriage, referral, diagnostic methods | |
| Mode of Administration | Postal | |
| Notes | Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Meadows 2000.
| Methods | Random allocation: method not specified | |
| Data | 600 diabetes patients aged 18 years or over selected from the patient register of a hospital outpatient diabetes centre in North England | |
| Comparisons | 1. High frequency response alternatives; Horizontal orientation of response options 2. Medium frequency response alternatives; Horizontal orientation of response options 3. High frequency response alternatives; Vertical orientation of response options | |
| Outcomes | Response period not specified | |
| Topic | Health: Diabetes health profile | |
| Mode of Administration | Postal | |
| Notes | The high frequency response alternatives are: Most days, Once a Week, Once a Month, Less Often, Never
The medium frequency response alternatives are: Once a Week or More Often, Once a Month, About Every Few Months, Less Often, Never Mean age: 52.2 years |
|
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Miller 1994.
| Methods | Random allocation: method not specified | |
| Data | Full‐time professors at doctorate granting or comprehensive universities | |
| Comparisons | 1. Incentive (decaffeinated coffee bag)
2. No incentive
3. Cover letter appeal: 'Your input into this matter is very important in determining what faculty consider scholarship to be'.
4. Cover letter appeal: 'It is important to ascertain what faculty consider scholarship to be, in order to develop models of scholarship and further knowledge' Follow up at 3 and 6 weeks after initial mailing |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Faculty attitudes about the personal importance of scholarly activities, institutional importance of scholarly activities, attitudes about faculty workload | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mizes 1984.
| Methods | Random allocation: method not specified | |
| Data | Physicians specialising in allergy randomly selected from all physicians listed under allergy or allergy/immunology in the telephone directory yellow pages of major metropolitan areas across the US | |
| Comparisons | 1. No incentive; Answer postcard 2. $1 cheque; Answer postcard 3. $5 cheque; Answer postcard 4. $1 cheque; Answer cheque 5. $5 cheque; Answer cheque |
|
| Outcomes | Response period not specified | |
| Topic | Health: Incidence, treatment, and the success of treatment of rhinitis melicamentosa | |
| Mode of Administration | Postal | |
| Notes | Method of allocation confirmed through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mond 2004.
| Methods | Random allocation: using random number generation in SPSS | |
| Data | Australian capital territory residents | |
| Comparisons | 1. Short questionnaire (8 pages long) 2. Long questionnaire (14 pages long) |
|
| Outcomes | Response period not specified | |
| Topic | Health: Measures of general psychological distress, disability, quality of life, eating disorders, exercise behaviours, healthcare utili sation etc. | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Morrison 2003.
| Methods | Random allocation: using random number generation in SPSS | |
| Data | Local residents | |
| Comparisons | 1. Study feedback information booklet 2. No information booklet |
|
| Outcomes | Response period not specified | |
| Topic | Health: Socio‐demographics, travel behaviour, risk perception, attitudes to the local area and health | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mortagy 1985.
| Methods | Random allocation: method not specified | |
| Data | Persons listed in electoral registers (Southampton and New Forest, UK) | |
| Comparisons | 1. Offered lottery ticket
2. Not offered lottery ticket Reminder sent to non‐respondents after 4 weeks |
|
| Outcomes | ||
| Topic | Health: Respiratory symptoms such as breathlessness, wheezing, cough, phlegm, hyperirritability of the bronchi; family illness; smoking habits; drug treatment | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Moses 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | Consultants identified from the Royal College of Obstetricians and Gynaecologists (RCOG) database | |
| Comparisons | 1. Prize draw incentive to win a personal digital assistant 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Current practice for the laparoscopic diagnosis and treatment of women with pelvic pain due to endometriosis | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Moss 1991.
| Methods | Random allocation: method not specified | |
| Data | Members of the National Council for Educational Measurement | |
| Comparisons | 1. Typed salutation; Metered return envelope 2. Typed salutation; Non‐metered return envelope 3. Hand‐written salutation; Metered return envelope 4. Hand‐written salutation; Non‐metered return envelope | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Respondents belief about the frequency and credibility of criticisms of standardized test | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mullen 1987.
| Methods | Random allocation: method not specified | |
| Data | Non‐federal office‐based members of the American Academy | |
| Comparisons | 1. Blue and white sticker incentive only
2. Withdrawal provision only
3. Incentive and withdrawal provision
4. No treatment Non‐respondents followed‐up 3 times |
|
| Outcomes | — | |
| Topic | Health: Counselling adult patients about smoking, weight, exercise, and stress, interest in continuing education | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Mullner 1982.
| Methods | Random allocation: method not specified | |
| Data | Community hospitals registered with the AHA (US) | |
| Comparisons | 1. Questionnaire in booklet form (QBF); Most salient and relevant question first (SRF); Cover letter personal in tone (CLP); Results promised (RP) 2. QBF; SRF; CLP; No RP 3. QBF; SRF; Cover letter impersonal in tone (CLI); RP 4. QBF; SRF; CLI; No RP 5. QBF; Salient and relevant questions last (SRL); CLP; RP 6. QBF; SRL; CLP; No RP 7. QBF; SRL; CLI; RP 8. QBF; SRL; CLI; No RP 9. Questionnaire in 2‐sided form style (QF); SRF; CLP; RP 10. QF; SRF; CLP; No RP 11. QF; SRF; CLI; RP 12. QF; SRF; CLI; No RP 13. QF; SRL; CLP; RP 14. QF; SRL; CLP; No RP 15. QF; SRL; CLI; RP 16. QF; SRL; CLI; No RP | |
| Outcomes | Response period not specified | |
| Topic | Health: Corporate planning, risk management programmes, expenditures for hospital supplies, admitting privileges of physicians, programmes of special services for the elderly | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Murawski 1996.
| Methods | Random allocation: method not specified | |
| Data | Veterans aged 60‐65 | |
| Comparisons | 1. Duke questionnaire
2. SF‐36 questionnaire
3. SIP questionnaire Follow ups sent 1 and 4 weeks |
|
| Outcomes | — | |
| Topic | Health: Health related quality of life (HRQoL) | |
| Mode of Administration | Postal | |
| Notes | Age: 60‐65 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Murphy 1991.
| Methods | Random allocation: alternation | |
| Data | International freight forwarders (US) | |
| Comparisons | 1. Pre‐notification postcard
2. No pre‐notification postcard Follow up sent after 3 weeks |
|
| Outcomes | Response within 62 days | |
| Topic | Non‐health: US industrial firm check | |
| Mode of Administration | Postal | |
| Notes | Age: 45‐48 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Myers 1969.
| Methods | Random allocation: method not specified | |
| Data | Households listed in a street order telephone directory (Los Angeles, US) | |
| Comparisons | 1. Pre‐contact letter 2. Questionnaire only 3. Questionnaire then follow‐up letter | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Reaction of public to various promotion efforts by the bank to establish the image of the bank | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nagata 1995.
| Methods | Random allocation: method not specified | |
| Data | Male owners of telephones (Gitu City, Japan) | |
| Comparisons | 1.
1‐page; Cigarette smoking and drinking
2.
2 pages; Cigarette smoking and drinking; Medical history
3.
2 pages; Cigarette smoking and drinking; Family history
4.
2 pages; Cigarette smoking and drinking; Family history; Consanguineous marriage
5.
3 pages; Cigarette smoking and drinking; Medical history; Family history; Consanguineous marriage
6. 2 pages; Cigarette smoking and drinking; Medical history; Family history; Consanguineous marriage Follow up in group 1 only |
|
| Outcomes | Response period not specified | |
| Topic | Health: Medical history, family history, smoking, drinking | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly 46‐65 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nakai 1997.
| Methods | Random allocation: alternation | |
| Data | People aged 40‐64 | |
| Comparisons | 1. Short questionnaire (4 pages) 2. Long questionnaire (8 pages) | |
| Outcomes | — | |
| Topic | Health: Health status, health related practice, smoking status | |
| Mode of Administration | Postal | |
| Notes | Age: 40‐64 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Napoles‐Springer 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | African American or White, who were at least 50 years old, and had once visited the primary care practices of an academic health centre during the previous year | |
| Comparisons | 1. Advance notice letter 2. No advance letter |
|
| Outcomes | Response period within 2 weeks | |
| Topic | Health: Patient satisfaction in adult ambulatory care | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Nederhof 1982.
| Methods | Random allocation: method not specified | |
| Data | All members of the general population of a medium‐sized Dutch town | |
| Comparisons | 1. Telephone pre‐notification 2. Mail pre‐notification | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nederhof 1983a.
| Methods | Random allocation: Using alternation | |
| Data | Group of members of the general public in Leyden, Netherlands | |
| Comparisons | 1. Computer‐printed address label 2. Hand‐written address label 3. Ball‐point pen worth $ 0.35 4. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes towards suicide | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nederhof 1983b.
| Methods | Random allocation: using alternation | |
| Data | Group of members of the general public in Leyden, Netherlands | |
| Comparisons | 1. Computer‐printed address label 2. Hand‐written address label |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes about females social roles and vegetarianism | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nederhof 1988.
| Methods | Random allocation: method not specified | |
| Data | Biotechnologists living in the Netherlands | |
| Comparisons | 1. Graphic illustration on cover of questionnaire largely in white 2. Graphic illustration on cover of questionnaire largely in black | |
| Outcomes | Response period not specified | |
| Topic | Health: Development in Biotechnology in the Netherlands | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Neider 1981a.
| Methods | Random allocation: method not specified | |
| Data | A sample of training and development directors who were members of the American Association for Training and Development | |
| Comparisons | 1. Hand addressed outgoing envelope 2. Typed outgoing envelope 3. Computer generated label on outgoing envelope | |
| Outcomes | Response period not specified | |
| Topic | Not specified. | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Neider 1981b.
| Methods | Random allocation: method not specified | |
| Data | A sample of Class I and II common carriers | |
| Comparisons | 1. Hand addressed outgoing envelope 2. Typed outgoing envelope 3. Computer generated label on outgoing envelope | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nevin 1975a.
| Methods | Random allocation: method not specified | |
| Data | Residents of university halls (US) | |
| Comparisons | 1. Given deadline of 5 days 2. Given deadline of 7 days 3. Given deadline of 9 days 4. No deadline given | |
| Outcomes | — | |
| Topic | Non‐health: Attitudes about residence halls | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nevin 1975b.
| Methods | Random allocation: method not specified | |
| Data | Non‐responders to earlier survey of university hall residents | |
| Comparisons | 1. Follow‐up letter with casual approach 2. Follow‐up letter with veiled threat | |
| Outcomes | Response within 18 days | |
| Topic | Non‐health: Attitudes about residence halls | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Newby 2003.
| Methods | Random allocation: computerised random number generation. | |
| Data | Businesses listed in Pert h, Western Australia | |
| Comparisons | 1. Monetary incentive worth A$20 2. Pre‐notification by telephone 3. Control |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes and expectations of the self‐employed | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Newland 1977.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in electoral register (Southampton, UK) | |
| Comparisons | 1. First class stamp on outgoing envelope; First class stamp on return envelope; White envelopes
2. Second class stamp on outgoing envelope; Second class envelope on return; White envelope
3. Second class frank on outgoing envelope; Second class business reply return envelope; White envelopes.
4. First class stamp on outgoing envelope; First class stamp on return envelope; Brown envelopes
5. Second class stamp on outgoing envelope; Second class envelope on return; Brown envelope
6. Second class frank on outgoing envelope; Second class business reply return envelope; Brown envelopes Follow up at 2 and 16 weeks including another copy of the questionnaire |
|
| Outcomes | — | |
| Topic | Health: Details of headache and accompanying symptoms, general health, demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nichols 1966.
| Methods | Random allocation: method not specified | |
| Data | College students who had returned a similar questionnaire 1 year previously | |
| Comparisons | 1. Follow‐up postcard after 3 days; Further follow‐up mailings 2. Not sent postcard after 3 days; Further follow‐up mailings | |
| Outcomes | Response within 120 days | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Nichols 1988.
| Methods | Random allocation: alternation. | |
| Data | Individuals listed on the electoral roll (Southampton, UK) | |
| Comparisons | 1. Information booklet sent 5 weeks before questionnaire 2. No information booklet sent | |
| Outcomes | Response period not specified | |
| Topic | Health: Nutritional health education leaflet | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Ogborne 1986.
| Methods | Random allocation: method not specified | |
| Data | Health and social service professionals who had not responded to an earlier mailing | |
| Comparisons | 1. Second questionnaires sent 2. Telephoned by a research assistant | |
| Outcomes | Response period not specified | |
| Topic | Health: Evaluation of innovative addiction assessment/referral programme | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Olivarius 1995.
| Methods | Random allocation: method not specified | |
| Data | GPs and specialists or consultants (Nordic countries) | |
| Comparisons | 1. Questionnaire received on a Friday (GPs)
2. Questionnaire received on a Monday (GPs)
3. Questionnaire received on a Friday (Specialists)
4. Questionnaire received on a Monday (Specialists) Follow ups sent after 14 and 28 days |
|
| Outcomes | Response within 60 days | |
| Topic | Health: Importance of GPs, treatment of general diseases | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Osborne 1996.
| Methods | Random allocation: method not specified | |
| Data | General practitioners | |
| Comparisons | 1. Received pre‐contact telephone call from non‐medical research assistant 2. No pre‐contact | |
| Outcomes | Response within 60 days | |
| Topic | Health: Views about pathological test ordering | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Paolillo 1984.
| Methods | Random allocation: systematic division | |
| Data | A sample of professionals from the Midwestern US | |
| Comparisons | 1. Control group 2. $1 enclosed with questionnaire 3. $2 promised on return of questionnaire 4. Entry into a lottery for a cash prize promised on return of questionnaire | |
| Outcomes | Response within 6 weeks | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Parasuraman 1981.
| Methods | Random allocation: method not specified | |
| Data | Commercial marketing research firms (US) | |
| Comparisons | 1. Brief cover letter 2. Detailed cover letter | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Aspects of marketing research | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Parkes 2000a.
| Methods | Random allocation: method not specified | |
| Data | Adults aged 20‐74 years who are cases or controls in a Canadian case‐control study of cancer | |
| Comparisons | 1. Enclosure of brochure with questionnaire which expands on the information provided in the covering letter about the survey 2. No brochure | |
| Outcomes | — | |
| Topic | Health: Tobacco exposure, diet, physical activity, use of medications, reproductive history | |
| Mode of Administration | Postal | |
| Notes | A reminder postcard, a reminder letter and second copy of the questionnaire and a follow‐up phone call were made 1‐2,4 and 6 weeks after the initial mailing, respectively, to non‐responders Age: 20‐74 year |
|
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Parkes 2000b.
| Methods | Random allocation: method not specified | |
| Data | Adults aged 20‐74 years who are controls in a Canadian case‐control study of cancer | |
| Comparisons | 1. No incentive 2. $2 sent with questionnaire 3. $5 sent with questionnaire | |
| Outcomes | — | |
| Topic | Health: Tobacco exposure, diet, physical activity, use of medications, reproductive history | |
| Mode of Administration | Postal | |
| Notes | A reminder postcard, a reminder letter and second copy of the questionnaire and a follow‐up phone call were made 1‐2,4 and 6 weeks after the initial mailing, respectively, to non‐responders Age: 20‐74 years |
|
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Parsons 1972a.
| Methods | Random allocation: method not specified | |
| Data | Alumni from a Masters in Business Administration Program at a private university | |
| Comparisons | 1. Pre‐notification 2. No pre‐notification | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Correlation between political opinions and religious belief | |
| Mode of Administration | Postal | |
| Notes | Allocation concealment ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Parsons 1972b.
| Methods | Random allocation: method not specified | |
| Data | Leaders of 2 religious sects (US) | |
| Comparisons | 1. Pre‐notification 2. No pre‐notification | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Correlation between political opinions and religious belief | |
| Mode of Administration | Postal | |
| Notes | Allocation concealment ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Paul 2005.
| Methods | Random allocation: computerised random number generation | |
| Data | Pharmacists in NSW, Australia who had sold Nicotine replacement therapy (NRT) or Bupropion in the last month | |
| Comparisons | 1. Gift voucher worth A$20 2. No voucher |
|
| Outcomes | Response period not specified | |
| Topic | Health: Smoking cessation | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Pearson 2003.
| Methods | Random allocation: using random number generated in Excel | |
| Data | Alumni at Stanford University | |
| Comparisons | 1. Salutation ‐ Generic (Dear Stanford Alumni) 2. Salutation ‐ Familiar personalis ation (Dear James) 3. Salutation ‐ Familiar personalis ation without the dear (James) 4. Salutation ‐ Formal personalised (Dear Mr. Bond) |
|
| Outcomes | Response within 27 days | |
| Topic | Non‐health: Stanford University's logos, image, and branding | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author; Age: Mostly 30‐49 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Peck 1981.
| Methods | Random allocation: method not specified | |
| Data | Men and women who had been high school juniors in spring 1973 (US) | |
| Comparisons | 1. Prepaid $3 incentive 2. Promised $3 incentive 3. No incentive | |
| Outcomes | Response within 5 weeks | |
| Topic | Non‐health: Career plans, labour market, post high school educational experience | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Perneger 1993.
| Methods | Random allocation: computerised random number generation | |
| Data | Young adults enrolled in various insurance plans (US) | |
| Comparisons | 1. No incentive
2. Reminder card
3. Money offer
4. Both incentives Follow up with the incentive found to be best after 14 days |
|
| Outcomes | Response within 80 days | |
| Topic | Health: Health status, risk taking behaviours, utilis ation of health services, satisfaction with health care, socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Age: Mostly 26‐30 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Perry 1974.
| Methods | Random allocation: alternation | |
| Data | Respondents to a previous questionnaire | |
| Comparisons | 1. Questionnaire sent in pre‐paid franked envelope 2. Questionnaire sent in hand‐stamped envelope | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Peters 1998.
| Methods | Random allocation: method not specified | |
| Data | People aged 35 and over registered with a general practice (Bristol, UK) | |
| Comparisons | 1. Telephone number requested 2. Telephone number not requested | |
| Outcomes | Response period not specified | |
| Topic | Health: Information about chronic conditions, socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Peterson 1975.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed in a telephone directory | |
| Comparisons | 1. University source (U); Outgoing envelope (OE) metered; Return envelope (RE) stamped; Follow‐up postcard (FUP); Address (A) typed 2. U; OE‐stamped; RE‐stamped; FUP; A‐typed 3. Business source (B); OE‐metered; RE‐stamped; FUP; A‐typed 4. B; OE‐stamped; RE‐stamped; FUP; A‐typed 5. U; OE‐metered; RE‐stamped; FUP; A‐label 6. U; OE‐stamped; RE‐stamped; FUP; A‐label 7. B; OE‐metered; RE‐stamped; FUP; A‐typed 8. B; OE‐stamped; RE‐stamped; FUP; A‐label 9. U; OE‐metered; RE‐stamped; No FUP; A‐typed 10. U; OE‐stamped; RE‐stamped; No FUP; A‐typed 11. B; OE‐metered; RE‐stamped; No FUP; A‐typed 12. B; OE‐stamped; RE‐stamped; No FUP; A‐typed 13. U; OE‐metered; RE‐stamped; No FUP; A‐label 14. U; OE‐stamped; RE‐stamped; No FUP; A‐label 15. B; OE‐metered; RE‐stamped; No FUP; A‐label 16. B; OE‐stamped; RE‐stamped' No FUP; A‐label 17. U; OE‐metered; RE‐Business reply (reply); FUP, typed 18. U; OE‐stamped; RE‐reply; FUP; A‐typed 19. B; OE‐metered; RE‐reply; FUP; A‐typed 20. B; OE‐stamped; RE‐reply; FUP; A‐typed 21. U; OE‐metered; RE‐reply; FUP; A‐label 22. U; OE‐stamped; RE‐reply; FUP; A‐label 23. B; OE‐metered; RE‐reply; FUP; A‐label 24. B; OE‐stamped; RE‐reply; FUP; A‐label 25. U; OE‐metered; RE‐reply; No FUP; typed 26. U; OE‐stamped; RE‐reply; No FUP; A‐typed 27. B; OE‐metered; RE‐reply; No FUP; A‐typed 28. B; OE‐stamped; RE‐reply; No FUP; A‐typed 29. U; OE‐metered; RE‐reply; No FUP; A‐label 30. U; OE‐stamped; RE‐reply; No FUP; A‐label 31. B; OE‐metered; RE‐reply; No FUP; A‐label 32. B; OE‐stamped; RE‐reply; No FUP; A‐label | |
| Outcomes | Response within 30 days | |
| Topic | Non‐health: Banking and financial attitudes | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Phillips 1951.
| Methods | Random allocation: method not specified | |
| Data | Graduates of Fisk University in the classes of 1924 and 1939 | |
| Comparisons | 1. Follow up by first class mail 2. Follow up by special delivery mail | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Pirotta 1999.
| Methods | Random allocation: method not specified | |
| Data | General practitioners | |
| Comparisons | 1. Sent primer postcard 5 days before questionnaire 2. Not sent primer postcard before questionnaire | |
| Outcomes | Response within 60 days | |
| Topic | Health: Not specified | |
| Mode of Administration | Postal | |
| Notes | Author contacted: additional unpublished data provided was slightly different to published report, author data included | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Poe 1988.
| Methods | Random allocation: method not specified | |
| Data | Relatives of people who had died and who's death certificates had been filed in September and October 1984 | |
| Comparisons | 1. 'Don't know' boxes included 2. 'Don't know' boxes not included | |
| Outcomes | Response period not specified | |
| Topic | Health: Health care in the last year of life, health practices, socio‐economics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Porter 2003a.
| Methods | Random allocation: using random number generated in SAS | |
| Data | Non‐applicant high school students | |
| Comparisons | 1. Control 2. $ 50 gift voucher for Amazon.com 3. $ 100 gift voucher for Amazon.com 4. $ 150 gift voucher for Amazon.com 5. $ 200 gift voucher for Amazon.com. |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Application to college | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Porter 2003b.
| Methods | Random allocation: using random number generated in SAS | |
| Data | Non‐applicant high school students | |
| Comparisons | 1. Salutations impersonal (e.g. Dear Student) 2. Salutations personal (e.g. Dear Jane) 3. Title of signatory, high (Director) 4. Title of signatory, low (Administrative assistant) 5. Sponsorship, low‐profile office (Office of Institutional Research) 6. Sponsorship, high‐profile office (Office of Admission) 7. Source of e‐mail address, office (e.g. surveyresearch@institution.edu) 8. Source of e‐mail address, person (e.g. jsmith@institution.edu) |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perceptions of the college and the reasons for not applying | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Porter 2005a.
| Methods | Random allocation: using random number generated in SAS | |
| Data | High school seniors who did not apply to the college | |
| Comparisons | 1. Subject‐line ‐ Blank 2. Subject‐line ‐ Survey 3. Subject‐line ‐ Liberal Arts University 4. Subject‐line ‐ Request for Assistance 5. Subject‐line ‐ Survey, Request for Assistance 6. Subject‐line ‐ Liberal Arts University, Request for Assistance 7. Subject‐line ‐ Liberal Arts University, Survey 8. Subject‐line ‐ Liberal Arts University, Request for Assistance, Survey |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health : Perceptions of the school | |
| Mode of Administration | Electronic : Online survey | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Porter 2005b.
| Methods | Random allocation: using random number generated in SAS | |
| Data | Undergraduates currently enrolled at the institution | |
| Comparisons | 1. Subject‐line ‐ Blank 2. Subject‐line ‐ Survey 3. Subject‐line ‐ Liberal Arts University 4. Subject‐line ‐ Request for Assistance 5. Subject‐line ‐ Survey, Request for Assistance 6. Subject‐line ‐ Liberal Arts University, Request for Assistance 7. Subject‐line ‐ Liberal Arts University, Survey 8. Subject‐line ‐ Liberal Arts University, Request for Assistance, Survey |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Abilities on various capabilities and types of knowledge | |
| Mode of Administration | Electronic: Online survey | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Porter S 2003b.
| Methods | Random allocation: using random number generated in SAS | |
| Data | Non‐applicant high school students | |
| Comparisons | 1. Selective statement in the e‐mail invitation 2. No selective statement in the e‐mail invitation 3. Mention of General deadline in at least 1 e‐mail 4. Mention of specific deadline in e‐mail 3 5. Mention of specific deadline in e‐mails 2 and 3 6. Mention of specific deadline in e‐mails 1,2, and 3 7. No general deadline 8. No specific deadline |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perceptions of the college and the reasons for not applying | |
| Mode of Administration | Electronic: Online survey | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Pourjalali 1994.
| Methods | Random allocation: random number table | |
| Data | Students who had participated in an investment game | |
| Comparisons | 1. Investigator perceived to be African‐American (AA); Male Investigator (MI); Informal letter (IL); Easier questions first (E1) 2. AA; MI; IL Harder questions first (H1) 3. AA; Female investigator (FI); IL; E1 4. AA; FI; IL; H1 5. AA; MI; Formal letter (FL); E1 6. AA; MI; FL; H1 7. AA; FI; FL; E1 8. AA; FI; FL; H1 9. Investigator perceived to beCaucasian (Ca); MI; IL; E1 10. Ca; MI; IL; H1 11. Ca; FI; IL; E1 12. Ca; FI; IL; H1 13. Ca; MI; FL; E1 14. Ca; MI; FL; H1 15. Ca; FI; FL; E1 16. Ca; FI; FL; H1 17. Investigator perceived to be Hispanic (Hi); MI; IL; E1 18. Hi; MI; IL; H1 19. Hi; FI; IL; E1 20. Hi; FI; IL; H1 21. Hi; MI; FL; E1 22. Hi; MI; FL; H1 23. Hi; FI; FL; E1 24. Hi; FI; FL; H1 25. Investigator perceived to be 'Foreign/Alien' (Fo); MI; IL; E1 26. Fo; MI; IL; H1 27. Fo; FI; IL; E1 28. Fo; FI; IL; H1 29. Fo; MI; FL; E1 30. Fo; MI; FL; H1 31. Fo; FI; FL; E1 32. Fo; FI; FL; H1 | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: AT&T investment game | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Equal male and females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Powers 1982.
| Methods | Random allocation: method not specified | |
| Data | High school juniors | |
| Comparisons | 1. Feedback offered; Long questionnaire 2. Feedback offered; Short questionnaire 3. No feedback offered; Long questionnaire 4. No feedback, Short questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Students reaction to the test administration and/or to the preparatory materials of SAT | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Pressley 1977.
| Methods | Random allocation: method not specified | |
| Data | Marketing research directors | |
| Comparisons | 1. Dime incentive included
2. No incentive
3. Cartoons
4. No cartoons
5. Yellow questionnaire
6. Blue questionnaire
7. Green questionnaire
8. White questionnaire Factorial design. Follow up sent to non‐respondents after 3 weeks |
|
| Outcomes | Response within 6 weeks. | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Pressley 1978.
| Methods | Random allocation: method not specified | |
| Data | Executives employed by organisations located throughout the US | |
| Comparisons | 1. Postscript; Deadline 2. No postscript; Deadline 3. Postscript; No deadline 4. No postscript; No deadline | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Pressley 1985.
| Methods | Random allocation: method not specified | |
| Data | Executives at VP‐level in firms employing more than 500 (US) | |
| Comparisons | 1. Mailed on Friday 2. Mailed on Monday 3. Coding hand‐written in black ink 4. Coding in invisible ink 5. Coding was typed room number 6. Telephone pre‐notification without incentive 7. Postcard pre‐notification with $0.10 incentive 8. Sent in window envelope 9. Sent in regular envelope | |
| Outcomes | Response within 2 weeks | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Price 1996.
| Methods | Random allocation: method not specified | |
| Data | A random sample of African‐American women from a Midwestern university minority alumni membership list | |
| Comparisons | 1. Race specific stamp on return envelope 2. General stamp on return envelope | |
| Outcomes | Response period not specified | |
| Topic | Health: Cervical cancer | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Price 2003.
| Methods | Random allocation: using alternation | |
| Data | Public health educators and University professors in Health Education who did not respond to the second mailing | |
| Comparisons | 1. Signed postcard 2. Unsigned postcard |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health education skills | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Pucel 1971.
| Methods | Random allocation: method not specified | |
| Data | Graduates (Minnesota, US) | |
| Comparisons | 1. Control 2. Pencil incentive 3. Coffee incentive 4. Green questionnaire 5. Pre‐notification letter 6. Pencil; Green questionnaire 7. Pencil; Pre‐notification letter 8. Pencil; Green questionnaire; Pre‐notification letter 9. Coffee incentive; Green questionnaire 10. Coffee incentive; Pre‐notification letter 11. Coffee incentive; Green questionnaire; Pre‐notification letter | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Criteria in counselling applicants to post high school vocational technical schools | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Puffer 2004.
| Methods | Random allocation: using random number generation in SPSS | |
| Data | Women who returned the risk factor questionnaire for Osteoporotic fracture | |
| Comparisons | 1. Single booklet ‐ 3 sections stapled together 2. Multiple booklet 3. SIngle‐sided 4. Double‐sided |
|
| Outcomes | Response period not specified | |
| Topic | Health: Patient‐based outcome measures concerned with Quality of Life (SF36, EQ5D) | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Renfroe 2002.
| Methods | Random allocation: method not specified | |
| Data | Participants of the AVID trial, USA | |
| Comparisons | 1. Mailed out by overnight express (OE); Certificate of appreciation included (CA); Mailed early (E); Signature of Principal Investigator on cover letter (PI) 2. OE; CA; E; Signature of Study Coordinator on cover letter (SC) 3. OE; CA; Mailed late (L); PI 4. OE; CA; L; SC 5. OE; No CA; E; PI 6. OE; No CA; E; SC 7. OE; No CA; L; PI 8. OE; No CA; L; SC 9. Mailed out by regular mail (RM); CA; E; PI 10. RM; CA; E; SC 11. RM; CA; L; PI 12. RM; CA; L; SC 13. RM; No CA; E; PI 14. RM; No CA; E; SC 15. RM; No CA; L; PI 16. RM; No CA; L; SC | |
| Outcomes | Response period not specified | |
| Topic | Health: Patient satisfaction | |
| Mode of Administration | Postal | |
| Notes | Mean age: 63; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Riesenberg 2006.
| Methods | Random allocation: method not specified | |
| Data | Designated Institutional Official (DIO) | |
| Comparisons | 1. Priority stamps worth $3.85 2. First‐class stamps worth $0.60 |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Employment ‐ Demographics, identification of roles and responsibilities, competencies, training and experience required by the DIO | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rikard‐Bell 2000.
| Methods | Random allocation: computerised random number generation | |
| Data | Dentists practising within the central Sydney area, Australia in 1997 | |
| Comparisons | 1. Advance telephone prompt 2. Advance letter prompt | |
| Outcomes | Response within 65 days | |
| Topic | Health: Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Rimm 1990.
| Methods | Random allocation: computerised random number generation | |
| Data | Male health professionals who had not responded to a previous questionnaire | |
| Comparisons | 1. Certified mail
2. United parcel service
3. Window envelope with personal return address
4. Typed address
5. Hand‐written address
6. Window envelope with computer printed address Factorial design |
|
| Outcomes | — | |
| Topic | Health: Medical history, current diet and lifestyle habits | |
| Mode of Administration | Postal. | |
| Notes | Method of allocation ascertained through contact with author; Age: 40‐75; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Roberts 1978.
| Methods | Random allocation: computerised random number generation | |
| Data | General practitioners who were members of the American Dental Association | |
| Comparisons | 1. Personalised; Social appeal; Deadline 2. Personalised; Social appeal; No deadline 3. Personalised; No social appeal; Deadline 4. Personalised; No social appeal; No deadline 5. Not personalised; Social appeal; Deadline 6. Not personalised, Social appeal; No deadline 7. Not personalised, No social appeal; Deadline 8. Not personalised, No social appeal; No deadline | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Informed that allocation concealment was adequate | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Roberts 1993.
| Methods | Random allocation: method not specified | |
| Data | Adults listed on a family health services authority register who had not responded to a previous questionnaire | |
| Comparisons | 1. First reminder was another copy of questionnaire 2. First reminder was a postcard | |
| Outcomes | Response period not specified | |
| Topic | Health: Health and lifestyle | |
| Mode of Administration | Postal | |
| Notes | Age: 16‐70 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roberts 1994.
| Methods | Random allocation: method not specified | |
| Data | Nurses (Auckland, New Zealand) | |
| Comparisons | 1. Brown re‐usable envelope out; Brown re‐usable envelope return
2. Brown re‐usable envelope out; White non‐reusable envelope return
3. White non‐reusable envelope out; Brown re‐usable envelope return
4. White non‐reusable envelope out; White non‐reusable envelope return Reminders sent using the same envelope combination as initially allocated |
|
| Outcomes | Response period not specified | |
| Topic | Health: Prevalence of back pain | |
| Mode of Administration | Postal | |
| Notes | Mean age: 37.5 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roberts 2000.
| Methods | Random allocation: method not specified | |
| Data | 1000 English women aged 40 to 65 years | |
| Comparisons | 1. Entry into lottery for prize draw of £50 on response 2. Direct payment of £5 on response 3. Entry into lottery and direct payment of £5 on response 4. No incentive | |
| Outcomes | Response within 3 months | |
| Topic | Health: Menopause services | |
| Mode of Administration | Postal | |
| Notes | Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roberts 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | General practices in the North and West Birmingham area | |
| Comparisons | 1. Lottery to win high street shopping voucher worth £100 2. Control |
|
| Outcomes | Response period not specified | |
| Topic | Health: Prevalence of IBS (Irritable Bowel Syndrome) using SF36, Rome II criteria | |
| Mode of Administration | Postal | |
| Notes | Mean age: 48 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Robertson 1978.
| Methods | Random allocation: method not specified | |
| Data | A systematic sample of Denver area residents listed in the Metropolitan area phone directory | |
| Comparisons | 1. Control; No incentive 2. Promise of $1 cash on return of questionnaire 3. Promise of $1 donation to charity on return of questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Robertson 2005.
| Methods | Random allocation: using alternation | |
| Data | Australian general practitioners and medical specialists | |
| Comparisons | 1. $ AU 2 scratch lottery ticket 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Heath: Exploring new drug use by GPs and Medical specialists | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Rolnick 1989.
| Methods | Random allocation: method not specified | |
| Data | Women with sexually transmitted diseases | |
| Comparisons | 1. Detailed questionnaire 2. Modified questionnaire | |
| Outcomes | Response within 2 months | |
| Topic | Health: Gynaecological issues | |
| Mode of Administration | Postal | |
| Notes | Age: 18‐28 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Romney 1993.
| Methods | Random allocation: method not specified | |
| Data | Community educators | |
| Comparisons | 1. Open‐ended format 2. Closed‐ended format | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Community educational needs assessment instrument | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ronckers 2004.
| Methods | Random allocation: method not specified | |
| Data | Dutch patients treated for ENT condition between 1945 and 1981 | |
| Comparisons | 1. Short questionnaire (8 pages) 2. Long questionnaire (12 pages) 3. Standard consent form 4. Multi‐option consent form (choices with regard to participation in 3 phases of the overall study) |
|
| Outcomes | Response period not specified | |
| Topic | Health: Female reproductive history, occupational exposures, and diet | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roscoe 1975.
| Methods | Random allocation: method not specified | |
| Data | Random sample of telephone customers | |
| Comparisons | 1. Long questionnaire; Postcard reminder follow up 2. Long questionnaire; Telephone reminder follow up 3. Short questionnaire; Postcard reminder follow up 4. Short questionnaire; Telephone reminder follow up | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Telephone behaviours, housing, mobility, demographics, socioeconomic characteristics | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rose 2007a.
| Methods | Random allocation: using random numbers chart | |
| Data | Employees of a large international retailer in the US | |
| Comparisons | 1. $1 bill 2. No incentive |
|
| Outcomes | Response period within 10 days | |
| Topic | Non‐health: Related to marketing skills, management, and leadership qualities | |
| Mode of Administration | Postal | |
| Notes | Surveys with incentives enclosed were identified by a one‐inch‐long, one‐fourth‐inch‐wide yellow highlighter mark within a half inch of both edges of the lower left corner of the back side of the survey. Also one‐fourth inch of the non highlighted corner at the bottom of the survey was cut off. | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rose 2007b.
| Methods | Random allocation: using random numbers chart | |
| Data | Employees of a large health care organisation in the US | |
| Comparisons | 1. Low novelty ‐ Plain bill 2. High Novelty ‐ Bill with small star sticker or Sacagawea gold dollar coin 3. A penny bill 4. A quarter bill 5. A dollar bill 6. No incentive |
|
| Outcomes | Response within 21 days | |
| Topic | Non‐health: Training needs | |
| Mode of Administration | Postal | |
| Notes | Surveys with incentives enclosed bears a one‐inch‐long, one‐fourth‐inch‐wide highlighted mark within a half inch of both edges of the lower left corner of the back side of the survey. Packets with pennies had orange marks, packets with quarters had yellow marks, packets with paper dollars had blue marks, and packets with sacagawea dollars had green highlighter marks. In addition, one‐fourth inch of the non highlighted corner at the bottom of the survey was cut off. | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rosoff 2005a.
| Methods | Random allocation: random block procedure | |
| Data | Childhood cancer survivors | |
| Comparisons | 1. Unconditional $10 bill 2. Conditional $10 bill |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health‐related behaviours among childhood cancer survivors and their parents | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rosoff 2005b.
| Methods | Random allocation: random block procedure | |
| Data | Childhood cancer survivors | |
| Comparisons | 1. Unconditional $10 bill 2. Conditional $10 bill |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health‐related behaviours among childhood cancer survivors and their parents | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rosoff 2005c.
| Methods | Random allocation: random block procedure | |
| Data | Parents of childhood cancer survivors | |
| Comparisons | 1. Unconditional $10 bill 2. Conditional $10 bill |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health‐related behaviours among childhood cancer survivors and their parents | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990a.
| Methods | Random allocation: method not specified | |
| Data | Students studying Wealth Accumulation Planning | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990b.
| Methods | Random allocation: method not specified | |
| Data | Students studying Financial Services: Environment and Professions | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990c.
| Methods | Random allocation: method not specified | |
| Data | Students studying Estate and Gift Tax Planning | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990d.
| Methods | Random allocation: method not specified | |
| Data | Students studying Wealth Accumulation Planning | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990e.
| Methods | Random allocation: method not specified | |
| Data | Students studying Economics | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990f.
| Methods | Random allocation: method not specified | |
| Data | Students studying Pensions and Other Retirement Plans | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990g.
| Methods | Random allocation: method not specified | |
| Data | Students studying Advanced Estate Planning | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990h.
| Methods | Random allocation: method not specified | |
| Data | Students studying Financial Statement Analysis | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990i.
| Methods | Random allocation: method not specified | |
| Data | Students studying Group Benefits and Social Insurance | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990j.
| Methods | Random allocation: method not specified | |
| Data | Students studying Planning for Business Owners and Professionals | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | ||
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990k.
| Methods | Random allocation: method not specified | |
| Data | Students studying Financial Statement Analysis | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990l.
| Methods | Random allocation: method not specified | |
| Data | Students studying Financial and Estate Planning | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990m.
| Methods | Random allocation: method not specified | |
| Data | Students studying Financial and Estate planning | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Roszkowski 1990n.
| Methods | Random allocation: method not specified | |
| Data | Students studying Group Benefits and Social Insurance | |
| Comparisons | 1. Long questionnaire
2. Short questionnaire Follow up sent to non‐respondents of first mailing |
|
| Outcomes | — | |
| Topic | Non‐health: Evaluation of the financial courses | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rucker 1979a.
| Methods | Random allocation: method not specified | |
| Data | Students | |
| Comparisons | 1. Standard questionnaire
2. Matrix questionnaire Follow up sent to non‐respondents after 10 days |
|
| Outcomes | Response within 2 months | |
| Topic | Non‐health: Attitudes towards purchasing clothes | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rucker 1979b.
| Methods | Random allocation: method not specified | |
| Data | Students | |
| Comparisons | 1. Standard questionnaire
2. Matrix questionnaire Follow up sent to non‐respondents after 10 days |
|
| Outcomes | Response within 1 month | |
| Topic | Non‐health: Clothing attitudes | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Rucker 1984.
| Methods | Random allocation: method not specified | |
| Data | Graduates | |
| Comparisons | 1. Textiles student sponsor; No photo of person on cover letter
2. Textiles student sponsor; Casually dressed person on cover letter
3. Textiles student sponsor; Formal dressed person on cover letter
4. Textiles professor sponsor; No photo of person on cover letter
5. Textiles professor sponsor; Casually dressed person on cover letter
6. Textiles professor sponsor; Formal dressed person on cover letter
7. Animal science student sponsor; No photo of person on cover letter
8. Animal science student sponsor; Casually dressed person on cover letter
9. Animal science student sponsor; Formal dressed person on cover letter
10. Animal science professor sponsor; No photo of person on cover letter
11. Animal science professor sponsor; Casually dressed person on cover letter
12. Animal science professor sponsor; Formal dressed person on cover letter Postcard reminder and second questionnaire sent to non ‐respondents at approximately bi‐monthly intervals |
|
| Outcomes | — | |
| Topic | Non‐health: Furniture opinion | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Russell 2003.
| Methods | Random allocation: computerised random number generation | |
| Data | Chiropractors registered with the College of Chiropractors of Alberta | |
| Comparisons | 1. Unconditional $5 bill 2. No incentive |
|
| Outcomes | Response period not specified | |
| Topic | Health: Immunis ation beliefs and behaviours of Chiropractors | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ryu 2006.
| Methods | Random allocation: using alternation | |
| Data | Detroit Area Study (DAS) 2001 | |
| Comparisons | 1. Cash ($5 bill) 2. In‐kind (set of passes to regional parks, or metro parks) |
|
| Outcomes | Response period not specified | |
| Topic | Health: Quality of life in the Metropolitan Detroit Area | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Saal 2005.
| Methods | Random allocation: using alternation | |
| Data | In‐patients admitted for elective surgery at the St. Gallen Cantonal Hospital | |
| Comparisons | 1. Questionnaire sent 1 week after discharge 2. Questionnaire sent 5 weeks after discharge 3. Questionnaire sent 9 weeks after discharge |
|
| Outcomes | Response period not specified | |
| Topic | Health: Patients assessment of anaesthesia care | |
| Mode of Administration | Postal | |
| Notes | Survey was conducted by an independent organisation ‐ The picker Institute | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Salim Silva 2002.
| Methods | Random allocation: method not specified | |
| Data | 2 female Australian samples. Sample A ‐ current office workers at a university. Sample B ‐ Patients seen by a consultant in rehab medicine | |
| Comparisons | 1. Telephone reminder 2. No telephone reminder | |
| Outcomes | — | |
| Topic | Health: Musculoskeletal symptoms, health service utilisation, tobacco and alcohol consumption, social support, occupational history and job satisfaction, general health, socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | Age: Mostly above 45 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Sallis 1984.
| Methods | Random allocation: method not specified | |
| Data | Physicians who had not responded to a previous questionnaire (Monterey County) | |
| Comparisons | 1. No incentive 2. Pencil incentive printed with an attractive design | |
| Outcomes | Response period not specified | |
| Topic | Health: Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Salvesen 1992.
| Methods | Random allocation: using a table of random numbers | |
| Data | Mothers who had not responded to a previous questionnaire | |
| Comparisons | 1. Newspaper article with description of the study 2. No article sent with the questionnaire | |
| Outcomes | Response within 30 days | |
| Topic | Health: Child's health ‐ hearing, vision | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Allocation was not concealed; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Sang‐Wook 2005.
| Methods | Random allocation: using random number generated in SAS | |
| Data | Korean‐Vietnam Veterans | |
| Comparisons | 1. Questionnaires sent via Recorded Delivery 2. Questionnaires sent via Standard Delivery 3. Stamped Return Envelope 4. Franked Return Envelop e |
|
| Outcomes | Response period not specified | |
| Topic | Health: Veterans socio‐economic and health status, medical check‐up | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Sauerland 2002.
| Methods | Random allocation: alternation | |
| Data | All members of the association of German surgeons | |
| Comparisons | 1. Hernia and Pain Questionnaires sent together in 1 letter 2. Hernia Questionnaire sent first, pain questionnaire sent 4 weeks later 3. Pain Questionnaire sent first, hernia questionnaire sent 4 weeks later | |
| Outcomes | Response period not specified | |
| Topic | Health: Perioperative pain management, Surgical technique in incisional hernia repair | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Schmidt 2005.
| Methods | Random allocation: using random number generated in SPSS | |
| Data | Product Development and Management Association (PDMA) members | |
| Comparisons | 1. Certified mail on outward mailing 2. First‐class mail on outward mailing |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Development of new products by various organisations | |
| Mode of Administration | Postal | |
| Notes | — | |
Schweitzer 1995.
| Methods | Random allocation: method not specified | |
| Data | University staff employed for at least 6 years (Pennsylvania, US) | |
| Comparisons | 1. Non‐form fillers; Paid in advance
2. Non‐form fillers; Paid on completion
3. Form‐fillers; Paid in advance
4. Non‐form fillers; Paid on completion Reminder sent to non‐respondents after 4 weeks |
|
| Outcomes | — | |
| Topic | Health: Knowledge, attitudes, and behaviours regarding the selection of employee health benefits | |
| Mode of Administration | Postal | |
| Notes | Age: 45‐48 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Scott 1957.
| Methods | Random allocation: alternation | |
| Data | Women aged 60 years and over from poll tax exemption lists for Travis County, Texas, USA, 1954 | |
| Comparisons | 1. Preliminary letter received on Monday, questionnaire received on Tuesday 2. Preliminary letter received on Monday, questionnaire received on Friday 3. No preliminary letter, questionnaire received on Wednesday 4. No preliminary letter, questionnaire received on Saturday | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Occupational history, present income/pension payment | |
| Mode of Administration | Postal | |
| Notes | Age: above 60 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
See Tai 1997.
| Methods | Random allocation: method not specified | |
| Data | Patients who had not responded to a questionnaire (London, UK) | |
| Comparisons | 1. Questionnaire reminder 2. Telephone reminder | |
| Outcomes | Response period not specified | |
| Topic | Health: to evaluate the use of structural computerised prompts in their management using Asthma Symptoms Questionnaire & Client Satisfaction Questionnaire (for patients with Asthma), and Well‐being Questionnaire and Diabetes Treatment Questionnaire ( for patients with Diabetics) | |
| Mode of Administration | Postal | |
| Notes | Mean age: Telephone group ‐ 47.5 years; Recorded delivery group ‐ 40 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Shackleton 1980.
| Methods | Random allocation: method not specified | |
| Data | Partially sighted school leavers aged between 17 and 20 years who had left schools for the visually handicapped during the previous academic year | |
| Comparisons | 1. £1 offered; previous examination 2. No incentive; previous examination 3. £1 offered; no examination 4. No incentive; no examination | |
| Outcomes | Response within 42 days | |
| Topic | Non‐health: Occupational experience during 1st year after leaving the school | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Age: 17‐20 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Shah 2001.
| Methods | Random allocation: method not specified | |
| Data | Patients aged 65 to 74 years in an inner London practice who had consulted within the last 2 years | |
| Comparisons | 1. Inclusion of questions on income; inclusion of consent form 2. Inclusion of questions on income; no consent form 3. No questions on income; inclusion of consent form 4. No questions on income; no consent form | |
| Outcomes | — | |
| Topic | Health: Physical and mental health, social circumstances, social support, living arrangements, income | |
| Mode of Administration | Postal | |
| Notes | Age: 65‐74 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Shahar 1993.
| Methods | Random allocation: method not specified | |
| Data | Individuals who had declined to participate in a previous study | |
| Comparisons | 1. Additional letter with first mailing requesting an explanation for not participating 2. No letter | |
| Outcomes | Response within 14 weeks | |
| Topic | Health: General health, physical activity, smoking habits, list of chronic disease, demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Sharp 2006.
| Methods | Random allocation: computerised random number generation | |
| Data | Participants from the TOMBOLA (Trial Of Management of Borderline and Other Low‐grade Abnormal smears) trial | |
| Comparisons | 1. Pen 2. No pen 3. First class dispatch 4. Second class dispatch 5. Freepost (business reply) envelope 6. Postage stamp envelope |
|
| Outcomes | Response period not specified | |
| Topic | Health: Psychosocial impact of having a low‐grade abnormal cervical smear and its subsequent management | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Shaw 2001.
| Methods | Random allocation: method not specified | |
| Data | HealthSystem Minnesota enrollees aged 20‐80 years | |
| Comparisons | 1. $5 included in survey package 2. $2 included in survey package | |
| Outcomes | — | |
| Topic | Health: Digestive Health Status instrument (DHS I), SF‐36, HADS, Comorbidity checklist, health care utilisation | |
| Mode of Administration | Postal | |
| Notes | Age: 20‐80 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Sheikh 1982.
| Methods | Random allocation: method not specified | |
| Data | 400 people who had completed an assessment course at an employment rehabilitation centre in London 1973‐1974 | |
| Comparisons | 1. Questionnaire including sensitive question on earnings 2. Same questionnaire as (1) without the sensitive question on earnings | |
| Outcomes | — | |
| Topic | Non‐health: Employment | |
| Mode of Administration | Postal | |
| Notes | Mean age: 39 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Shin 1992.
| Methods | Random allocation: method not specified | |
| Data | Faculty members in universities and 4 year colleges in the United States | |
| Comparisons | 1. Personalised (P); anonymous (A); professional appeal (Prof); university sponsored (U) questionnaire 2. P; A; Prof; Private research institute sponsored (PR) 3. P; A; personal appeal (Pers); U 4. P; A; Pers; PR 5. P; Nonanonymous (NA); Prof; U 6. P; NA; Prof; PR 7. P; NA; Pers; U 8. P; NA; Pers; PR 9. Not Personalised (Not P); A; Prof; U 10. Not P; A; Prof; PR 11. Not P; A; Pers; U 12. Not P; A; Pers; PR 13. Not P; NA; Prof; U 14. Not P; NA; Prof; PR 15. Not P; NA; Pers; U 16. Not P; NA; Pers; PR | |
| Outcomes | Response within 7 weeks | |
| Topic | Non‐health: Student evaluation of faculty instruction | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Shiono 1991.
| Methods | Random allocation: method not specified | |
| Data | Physicians (US) | |
| Comparisons | 1. Pre‐notification letter; Stamp on return envelope 2. Pre‐notification letter; Return envelope franked 3. No pre‐notification letter; Stamp on return envelope 4. No pre‐notification letter; Return envelope franked | |
| Outcomes | ||
| Topic | Health: Pregnancy among resident physicians | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Simon 1967a.
| Methods | Random allocation: alternation | |
| Data | Readers of an magazine published by a national industrial company | |
| Comparisons | 1. Personal letter 2. Form letter | |
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes towards a hospital insurance plan | |
| Mode of Administration | Postal | |
| Notes | Author contacted: unable to provide further details on randomisation | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Simon 1967b.
| Methods | Random allocation: alternation | |
| Data | Readers of an magazine published by a national industrial company | |
| Comparisons | 1. Personal letter 2. Form letter | |
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes towards a hospital insurance plan | |
| Mode of Administration | Postal | |
| Notes | Author contacted: unable to provide further details on randomisation | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Simon 1967c.
| Methods | Random allocation: alternation | |
| Data | Subscribers to a hospital insurance plan | |
| Comparisons | 1. Personal letter 2. Form letter | |
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes towards a hospital insurance plan | |
| Mode of Administration | Postal | |
| Notes | Author contacted: unable to provide further details on randomisation | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Skinner 1984.
| Methods | Random allocation: method not specified | |
| Data | Marketing professors, Canada | |
| Comparisons | 1. No incentive 2. $1 pre‐paid incentive 3. $1 promised incentive; Respondent identified 4. $1 promised incentive; Respondent not identified 5. $1 promised to charity | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Needs of Canadian instructors regarding an introductory marketing text | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Sletto 1940.
| Methods | Random allocation: alternation | |
| Data | Former university students | |
| Comparisons | 1. 10‐page questionnaire; Altruistic appeal in cover letter 2. 10‐page questionnaire; Cover letter requesting help 3. 10‐page questionnaire; Cover letter challenging participants to respond 4. 25‐page questionnaire; Altruistic appeal in cover letter 5. 25‐page questionnaire; Cover letter requesting help 6. 25‐page questionnaire; Cover letter challenging participants to respond 7. 35‐page questionnaire ( 10 and 25‐page questionnaires); Altruistic appeal in cover letter 8. 35‐page questionnaire ( 10 and 25‐page questionnaires); Cover letter requesting help 9. 35‐page questionnaire ( 10 and 25‐page questionnaires); Cover letter challenging participants to respond | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Vocational activities, needs, interest, socio‐civic activities | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Sloan 1997.
| Methods | Random allocation: method not specified | |
| Data | Doctors of patients with cancer | |
| Comparisons | 1. University letterhead (UL); MD signatory (MD); Hand‐written note (HN)
2. Cancer agency letterhead (CL); MD; HN
3. UL; PhD signatory (PhD), HN
4. CL; PhD; HN
5. UL; MD; No HN
6. CL; MD; No HN
7. UL; PhD, No HN
8. CL; PhD, No HN NB: this was a letter requesting doctors to give consent for patients to be contacted and sent questionnaires |
|
| Outcomes | Response period not specified | |
| Topic | Health: Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Smith 1985.
| Methods | Random allocation: sequential sampling | |
| Data | Patients aged 40‐59 years registered with an urban general practice, UK | |
| Comparisons | 1. Questionnaire sent by General Practitioner 2. Questionnaire sent by a Doctor from the research unit | |
| Outcomes | Response within 9 weeks | |
| Topic | Health: Aggression scale, Social desirability scale, Fear survey schedule II, Situations evoking social anxiety scale, Social evaluative anxiety scale | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Spry 1989a.
| Methods | Random allocation: using a table of random numbers | |
| Data | Residences listed in the Haines Directory (San Diego, US) | |
| Comparisons | 1. Telephone pre‐notification; Lottery entry offer 2. Telephone pre‐notification; No lottery offer 3. Postcard pre‐notification; Lottery entry offer 4. Postcard pre‐notification; No lottery offer 5. No pre‐notification; Lottery entry offer 6. No pre‐notification; No lottery offer | |
| Outcomes | Response period not specified | |
| Topic | Health: Health and physical activity habits | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Randomisation not concealed; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Spry 1989b.
| Methods | Random allocation: using a table of random numbers | |
| Data | Residences listed in the Haines Directory (San Diego, US) | |
| Comparisons | 1. Short questionnaire; Lottery 2. Short questionnaire; No lottery 3. Long questionnaire; Lottery 4. Long questionnaire; No lottery | |
| Outcomes | Response period not specified | |
| Topic | Health: Health and physical activity habits | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Randomisation not concealed; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Spry 1989c.
| Methods | Random allocation: using a table of random numbers | |
| Data | Residences listed in the Haines Directory who had not responded to a questionnaire (San Diego, US) | |
| Comparisons | 1. Promise of $5 when respond 2. Promise of $1 when respond 3. $1 bill enclosed 4. No incentive | |
| Outcomes | Response period not specified | |
| Topic | Health: Health and physical activity habits | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author. Randomisation not concealed; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Stafford 1966.
| Methods | Random allocation: method not specified | |
| Data | University students (Houston, US) | |
| Comparisons | 1. Pre‐notification letter sent 2. Pre‐notification telephone call made 3. No pre‐notification contact | |
| Outcomes | — | |
| Topic | Non‐health: Collegiate clothing market | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Stapulonis 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | Members form the Welfare‐to‐Work evaluation site at Chicago | |
| Comparisons | 1. Conditional $20 check 2. Conditional point‐of‐sale cards worth $20 |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Employment | |
| Mode of Administration | Electronic: Computer Assisted Telephone Interview (CATI) | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Stem 1984a.
| Methods | Random allocation: using random number table | |
| Data | Students | |
| Comparisons | 1. Randomised response model 2. Direct questions |
|
| Outcomes | Response period not specified | |
| Topic | Non ‐health: Cheating behaviours during exams | |
| Mode of Administration | Postal | |
| Notes | — | |
Stem 1984b.
| Methods | Random allocation: using random number table | |
| Data | Automobile sales license holders | |
| Comparisons | 1. Randomised response model 2. Direct questions |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Automobile selling practices | |
| Mode of Administration | Postal | |
| Notes | — | |
Stevens 1975.
| Methods | Random allocation: alternation | |
| Data | Graduates from a southern university (US) | |
| Comparisons | 1. Pre‐coded questionnaire 2. Questionnaire not pre‐coded | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Job hunting experience | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Streiff 2001.
| Methods | Random allocation: alternation | |
| Data | Randomly selected members of the American Society of Hematology | |
| Comparisons | 1. Business reply envelope 2. Stamped return envelope | |
| Outcomes | Response within 3 months | |
| Topic | Health: Diagnosis and treatment of polycythaemia Vera | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Subar 2001.
| Methods | Random allocation: method not specified | |
| Data | 900 control participants from 3 centres in the prostate, lung, colorectal and ovarian cancer screening trial | |
| Comparisons | 1. Diet history questionnaire ‐ 36 pages 2. Food frequency questionnaire ‐ 16 pages | |
| Outcomes | — | |
| Topic | Health: Food frequency questionnaire, Diet history questionnaire | |
| Mode of Administration | Postal | |
| Notes | Age: 55‐74 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Sutton 1992.
| Methods | Random allocation: method not specified | |
| Data | Business customers who had taken advantage of an earlier rebate programme | |
| Comparisons | 1. Pre‐notification postcard; Prior telephone call 2. Pre‐notification postcard; No prior telephone call 3. No pre‐notification postcard; No prior telephone call 4. No pre‐notification postcard; No prior telephone call | |
| Outcomes | Response period within 43 days | |
| Topic | Non‐health: Customer reaction to energy rebate programme | |
| Mode of Administration | Postal | |
| Notes | Author contacted: reported adequate allocation concealment | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Svoboda 2001.
| Methods | Random allocation: central randomisation | |
| Data | Head injured adults in the CRASH trial (Czech Republic) | |
| Comparisons | 1. 1‐page questionnaire 2. 3‐ page questionnaire | |
| Outcomes | Response within 3 months | |
| Topic | Health: Disability after traumatic brain injury | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Swan 1980.
| Methods | Random allocation: method not specified | |
| Data | Individuals who had not responded to an earlier questionnaire | |
| Comparisons | 1. Follow‐up letter only 2. Follow‐up letter and questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perception of educational needs for the real estate profession, sale management practices, business planning, information about respondents firm | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Szirony 2002.
| Methods | Random allocation: using random table of numbers | |
| Data | Faculty members from the top 100 graduate degree granting institutions in Nursing | |
| Comparisons | 1. Cover letter signed by a graduate student 2. Cover letter signed by a faculty member |
|
| Outcomes | Response period not specified | |
| Topic | Health: Publication, authorship, reporting of research results, funding, demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | Inadequate |
Tamayo‐Sarver 2004.
| Methods | Random allocation: using random number generated in STATA | |
| Data | Practicing Physicians with American College of Emergency Physicians membership | |
| Comparisons | 1. $2 bill 2. Lottery to win $250 |
|
| Outcomes | Response period not specified | |
| Topic | Health: Diagnosis and treatment plan; practice environment | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Tambor 1993.
| Methods | Random allocation: method not specified | |
| Data | Physicians (US) | |
| Comparisons | 1. Continuing medical education credits 2. No credits | |
| Outcomes | Response period not specified | |
| Topic | Health: Genetic knowledge, psychometric scales, demographics | |
| Mode of Administration | Postal | |
| Notes | Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Taylor 1998.
| Methods | Random allocation: stratified random sampling method | |
| Data | Young people in the Youth Cohort Study 8 sample, England | |
| Comparisons | 1. Preliminary notice letter 2. No preliminary notification | |
| Outcomes | Response within approximately 2 months | |
| Topic | Non‐health: Attitudes and behaviour while transition from secondary school to labour market / tertiary education system | |
| Mode of Administration | Postal | |
| Notes | Mean age: 16.5 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Taylor 2006.
| Methods | Random allocation: computerised random number generation | |
| Data | Participants registered in general practices in Aberdeen | |
| Comparisons | 1. Questionnaire printed in black ink 2. Questionnaire printed in green ink 3. Questionnaire sent in white envelope 4. Questionnaire sent in brown envelope |
|
| Outcomes | Response period within 6 months | |
| Topic | Health: Screening questions for Parkinsonism; EuroQuol EQ5D | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Teisl 2005.
| Methods | Random allocation: using random number generated in Excel | |
| Data | US residents | |
| Comparisons | 1. $1 cash 2. $2 cash 3. Phone card worth $2 4. Phone card worth $5 |
|
| Outcomes | Response period not specified | |
| Topic | Health: General perception of food and food processing, knowledge, and attitudes towards genetically modified foods | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Temple‐Smith 1998.
| Methods | Random allocation: method not specified | |
| Data | General practitioners | |
| Comparisons | 1. Pre‐contact by GP researcher 2. Pre‐contact by non‐medical researcher (older woman) 3. Pre‐contact by non‐medical researcher (younger woman) 4. Pre‐contact by non‐medical researcher (younger man) | |
| Outcomes | Response within 8 weeks | |
| Topic | Health: Knowledge, attitudes, behaviour, and practice (KABP) in relation to Sexually Transmitted Diseases | |
| Mode of Administration | Postal | |
| Notes | Age: Above 65 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Thistlethwaite 1993.
| Methods | Random allocation: method not specified | |
| Data | People aged 65 years and over from 7 counties in a Midwestern state of the USA | |
| Comparisons | 1. No offer of results (NO); Altruistic appeal (A); No demographic omission (No D) 2. NO; A; Demographic Omission (D) 3. NO; Egoistic Appeal (E); No D 4. NO; E; D 5. Offer of results (O); A; No D 6. O; A; D 7. O; E; No D 8. O; E; D | |
| Outcomes | Response within 4 weeks | |
| Topic | Non‐health: Characteristics most desired in retirement centre, leisure time activities | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author; Age: Above 65 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Thomson 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | Practising GPs in Lothian, Scotland | |
| Comparisons | 1. Lottery to win 6 bottles of champagne 2. Lottery to win 1 bottle of champagne |
|
| Outcomes | Response period not specified | |
| Topic | Health: GPs opinions on toe nail surgery services offered by Podiatrists and Surgeons | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | Adequate |
Tjerbo 2005.
| Methods | Random a llocation: method not specified | |
| Data | Medical practitioners in Norway | |
| Comparisons | 1. Unconditional scratch lottery 2. Conditional lottery to win a holiday trip worth 8,000 Norwegian Kronner 3. Control |
|
| Outcomes | — | |
| Topic | Health: Relationship between primary care and secondary care | |
| Mode of Administration | Postal | |
| Notes | Language of publication is Norwegian | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Trussell 2004a.
| Methods | Random allocation: method not specified | |
| Data | Households in the designated market area in the US who agreed to participate in the mail survey during the screening telephone survey | |
| Comparisons | 1. No incentives 2. One $1 bill 3. Two $1 bills 4. Three $1 bills 5. Four $1 bills 6. Five $1 bills 7. Six $1 bills 8. Seven $1 bills 9. Eight $1 bills 10. Ten $1 bills. |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Television viewing | |
| Mode of Administration | Postal | |
| Notes | Larger incentive: From one $1 bill to five $1 bills; Smaller incentive: From six one $1 bills to ten $1 bills | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Trussell 2004b.
| Methods | Random allocation: method not specified | |
| Data | Households in the designated market area in the US who were unable to contact during the screening telephone survey | |
| Comparisons | 1. No incentives 2. One $1 bill 3. Two $1 bills 4. Three $1 bills 5. Four $1 bills 6. Five $1 bills 7. Six $1 bills 8. Seven $1 bills 9. Eight $1 bills 10. Ten $1 bills |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Television viewing | |
| Mode of Administration | Postal | |
| Notes | Larger incentive : From one $1 bill to five $1 bills; Smaller incentive: From six one $1 bills to ten $1 bills | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Trussell 2004c.
| Methods | Random allocation: method not specified | |
| Data | Households in the designated market area in the US who refused to participate in the mail survey during the screening telephone survey | |
| Comparisons | 1. No incentives 2. One $1 bill 3. Two $1 bills 4. Three $1 bills 5. Four $1 bills 6. Five $1 bills 7. Six $1 bills 8. Seven $1 bills 9. Eight $1 bills 10. Ten $1 bills |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Television viewing | |
| Mode of Administration | Postal | |
| Notes | Larger incentive : From one $1 bill to five $1 bills; Smaller incentive: From six one $1 bills to ten $1 bills | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Tullar 1979.
| Methods | Random allocation: method not specified | |
| Data | Large manufacturing firms | |
| Comparisons | 1. No follow up; No incentive 2. No follow up; 10 cents incentive 3. Follow up; No incentive 4. No follow up; 10 cents incentive | |
| Outcomes | Response within 8 weeks | |
| Topic | Non‐health: Time for development of new product | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Tullar 2004.
| Methods | Random allocation: computerised random number generation | |
| Data | Medicare recipients who underwent total hip replacement in 1995 | |
| Comparisons | 1. Hand‐written addresses in the envelope of all outgoing mails 2. Computer‐printed addresses in the envelope of all outgoing mails 3. Hand stamped envelopes 4. Institutionally metered postage |
|
| Outcomes | Response period not specified | |
| Topic | Health: pain, functional status, satisfaction, complication, general health | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Tuten 2004.
| Methods | Random allocation: method not specified | |
| Data | Unemployed Croatians | |
| Comparisons | 1. No incentives 2. Offer of study results 3. Lottery of 1000 Kuna with immediate notification of the results 4. Lottery of 1000 Kuna with delayed (after 1 month) notification of the results |
|
| Outcomes | Response period not specified | |
| Topic | Health: Psychosocial consequences of unemployment | |
| Mode of Administration | Electronic: Online survey | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ulrich 2005.
| Methods | Random allocation: computerised random number generation | |
| Data | Nurse practitioners and physician assistants practising in primary care in the US | |
| Comparisons | 1. No incentive 2. Unconditional $5 prepaid token incentive 3. Conditional lottery to win one of ten $100 prize draw |
|
| Outcomes | Response period not specified | |
| Topic | Health: Ethical concerns in the course of practice | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Urban 1993.
| Methods | Random allocation: method not specified | |
| Data | Physicians providing primary care | |
| Comparisons | 1. Return envelope with first class stamp 2. Business reply return envelope | |
| Outcomes | Response within 6 weeks | |
| Topic | Health: Attitudes, beliefs, and practices regarding regular breast cancer screening | |
| Mode of Administration | Postal | |
| Notes | Age: 50‐75 years; Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
VanGeest 2001.
| Methods | Random allocation: method not specified | |
| Data | Physicians randomly selected from the American Medical Association's master file of all physicians practising in the US | |
| Comparisons | 1. $5 cash incentive 2. $10 cash incentive 3. $20 cash incentive | |
| Outcomes | Response period not specified | |
| Topic | Health: Attitudes and responses in relation to utilisation and review pressure | |
| Mode of Administration | Postal | |
| Notes | Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Veiga 1974.
| Methods | Random allocation: method not specified | |
| Data | Randomly selected managers | |
| Comparisons | 1. Stamped return envelope 2. Business reply return envelope 3. Internal mail return | |
| Outcomes | Response within 4 weeks | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Virtanen 2007a.
| Methods | Random allocation: using split‐panel design | |
| Data | Working‐age population living in rural areas in Finland | |
| Comparisons | 1. SMS reminder 2. Traditional post‐card reminder |
|
| Outcomes | Response period within 28 days | |
| Topic | Non‐health: Information and Computer Technology (ICT) usage | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Virtanen 2007b.
| Methods | Random allocation: using split‐panel design | |
| Data | Welfare and health professionals in Finland | |
| Comparisons | 1. SMS reminder 2. Traditional post‐card reminder |
|
| Outcomes | Response period within 28 days | |
| Topic | Health: Working and welfare conditions of health and social care workers | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Virtanen 2007c.
| Methods | Random allocation: using split‐panel design | |
| Data | Members of trade union in Finland | |
| Comparisons | 1. SMS reminder 2. Traditional post‐card reminder |
|
| Outcomes | Response period within 28 days | |
| Topic | Non‐health: Employment | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Vocino 1977.
| Methods | Random allocation: method not specified | |
| Data | Members of the American Society for Public Administration | |
| Comparisons | 1. Metered envelope
2. Commemorative stamp
3. Deadline
4. No deadline
5. Cover letter by well‐known person in the discipline
6. Cover letter by unknown person in the discipline Factorial design |
|
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Vogel 1992.
| Methods | Random allocation: method not specified | |
| Data | Individuals treated at an alcohol and drug treatment centre (Norway) | |
| Comparisons | 1. Short questionnaire; Lottery ($70) incentive if respond
2. Short questionnaire; No lottery incentive
3. Long questionnaire; Lottery ($70) incentive if respond
4. Long questionnaire; No lottery incentive Follow up after 7 months |
|
| Outcomes | Response period not specified | |
| Topic | Health: Post‐discharge alcohol use, health status | |
| Mode of Administration | Postal | |
| Notes | Mean age: 42.4 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
VonRiesen 1979.
| Methods | Random allocation: method not specified | |
| Data | Veterinarians (Texas, US) | |
| Comparisons | 1. Postcard reminders 8 days after initial mailing 2. Second copy of questionnaire, with cover letter and business reply envelope, 8 days after initial mailing 3. No follow up | |
| Outcomes | Response period not specified | |
| Topic | Health: Supplier configuration, reasons for patronage, dollar amounts of annual purchases | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Waisanen 1954.
| Methods | Random allocation: alternation | |
| Data | Equal numbers of families owning and not owning television sets | |
| Comparisons | 1. Telephone pre‐contact 2. No telephone pre‐contact | |
| Outcomes | Response within 10 days | |
| Topic | Non‐health: Self‐rating of personal possession, occupation, television, income, education | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Walker 1997.
| Methods | Random allocation: method not specified | |
| Data | General population controls in a leg ulcer study aged 40‐99 years, randomly selected from the electoral roll, Auckland, New Zealand | |
| Comparisons | 1. Glossy brochure enclosed 2. No glossy brochure | |
| Outcomes | Response by post | |
| Topic | Health: SF‐36, HRQoL (Leg ulcers) | |
| Mode of Administration | Postal | |
| Notes | Age: 40‐90 years | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Waltemyer 2005.
| Methods | Random allocation: method not specified | |
| Data | National Collegiate Athletic Association (NCAA) Division I and III assistant softball coaches | |
| Comparisons | 1. Signed cover letter 2. Unsigned cover letter 3. White questionnaire 4. Yellow questionnaire |
|
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ward 1996.
| Methods | Random allocation: method not specified | |
| Data | Patients from a metropolitan general practice (Sydney, Australia) | |
| Comparisons | 1. $1 'scratchy' incentive with questionnaire
2. No incentive Follow up sent at 21 and 30 days |
|
| Outcomes | Response within 30 days | |
| Topic | Health: SF‐36, patient satisfaction, risk factors, chronic diseases | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Ward 1998.
| Methods | Random allocation: method not specified | |
| Data | Registered medical practitioners who had at least 1500 consultations per year | |
| Comparisons | 1. Exhaustive pre‐contact by telephone (continued until spoke to GP)
2. Gold pen incentive; University of NSW logo attached to questionnaire
3. Pre‐contact letter with University of NSW crests Follow‐ up letter sent after 16 days to non‐respondents. Second questionnaire sent after 23 days Telephone prompt from a non‐medical research assistant after 39 days |
|
| Outcomes | — | |
| Topic | Health: Cancer screening, personal and family history of cancer, socio‐ demographics | |
| Mode of Administration | Postal | |
| Notes | Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Warriner 1996.
| Methods | Random allocation: method not specified | |
| Data | Households listed in the Grand River Watershed region of south‐western Ontario, Canada | |
| Comparisons | 1. Monetary incentive
2. No monetary incentive
3. Offer to make a charitable donation or lottery
4. No offer Factorial design |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Environmental issues | |
| Mode of Administration | Postal | |
| Notes | Author contacted: allocation was not concealed | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Weilbacher 1952.
| Methods | Random allocation: method not specified | |
| Data | University alumni members (Columbia, US) | |
| Comparisons | 1. Personalised letter of transmittal 2. Non personalised letter of transmittal | |
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Weir 1999.
| Methods | Random allocation: computer algorithm | |
| Data | Patients with cerebrovascular disease discharged from hospital | |
| Comparisons | 1. Questionnaire sent via GP 2. Questionnaire sent direct to participants by research group | |
| Outcomes | — | |
| Topic | Health: Stroke outcomes | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wells 1984.
| Methods | Random allocation: method not specified | |
| Data | University undergraduates | |
| Comparisons | 1. University sponsor; Business reply return envelope 2. University sponsor; No return postage 3. IRE sponsor; Business reply return envelope 4. IRE sponsor; No return postage | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitude measure ‐ degree of satisfaction with the university's contribution to personal development | |
| Mode of Administration | Postal | |
| Notes | Mainly females | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Weltzien 1986.
| Methods | Random allocation: method not specified | |
| Data | Individuals who had terminated from mental health treatment centres | |
| Comparisons | 1. 2 cents incentive with questionnaire 2. No incentive | |
| Outcomes | Response within 4 months | |
| Topic | Health: Consumer Satisfaction Questionnaire (CSQ) | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wensing 1999a.
| Methods | Random allocation: method not specified | |
| Data | Adult patients who had visited a GP | |
| Comparisons | 1. Postal reminders
2. No reminders sent Reminder questionnaires sent at 3 weeks |
|
| Outcomes | — | |
| Topic | Health: Europep ‐ Patients evaluation of general practice care | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wensing 1999b.
| Methods | Random allocation: method not specified | |
| Data | Adult patients who had visited a GP | |
| Comparisons | 1. Postal reminders
2. No reminders sent Reminder questionnaires sent at 3 weeks |
|
| Outcomes | — | |
| Topic | Health: Europep ‐ Patients evaluation of general practice care | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wensing 2005.
| Methods | Random allocation: computerised random number generation | |
| Data | Elderly adults registered with 26 general practitioners in the Netherlands | |
| Comparisons | 1. Simple reminder card 2. Reminder + questionnaire 3. Reminder with request to explain nonparticipation |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health problems, health information sought, and attendance of general practice | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Whitcomb 2004.
| Methods | Random allocation: method not specified | |
| Data | High school students who did not apply to the Liberal Arts College | |
| Comparisons | 1. E‐mail file format ‐ Text 2. E‐mail file format ‐ HTML 3. Background colour ‐ White 4. Background colour ‐ Black 5. Graphical design (Header) ‐ Simple (Institution name only) 6. Graphical design (Header) ‐ Complex (Mimicked University homepage ‐ institutions name, campus photograph, quotation from the University president) |
|
| Outcomes | Response period not specified | |
| Topic | Non‐health: Perception of the college, reason for not applying | |
| Mode of Administration | Electronic: Web‐survey | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
White 1997.
| Methods | Random allocation: method not specified | |
| Data | A random sample of marriage and family therapists from a list of all approved supervisors of the American Association of Marriage and Family Therapy | |
| Comparisons | 1. Personalised cover letter; White questionnaire 2. Personalised cover letter; Blue questionnaire 3. Generic cover letter; White questionnaire 4. Generic cover letter; Blue questionnaire | |
| Outcomes | Response period not specified | |
| Topic | Health: Demographics, Marriage and Family Therapist's supervision | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
White 2005a.
| Methods | Random allocation: method not specified | |
| Data | Participants from the New Hampshire Women for Health (NHWH) study | |
| Comparisons | 1. Inclusion of a pen in the second mailing study 2. No penin the second mailing study |
|
| Outcomes | Response period within 60 days | |
| Topic | Health: Hormone replacement therapy, breast cancer, health‐related quality of life | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
White 2005b.
| Methods | Random allocation: method not specified | |
| Data | Vanguard participants from the 13 counties of Western Washington State | |
| Comparisons | 1. Inclusion of a pencil in the second mailing study 2. No pencil in the second mailing study |
|
| Outcomes | Response period not specified | |
| Topic | Health: Vitamins and lifestyle | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Whiteman 2003.
| Methods | Random allocation: computerised random number generation | |
| Data | Women in the Baltimore Metropolitan area who reported their history of hot flashes | |
| Comparisons | 1. Introductory postcard mailed 1 week before the questionnaire 2. Scratch‐off lottery ticket worth $1.00 3. $1 bill 4. No incentives |
|
| Outcomes | Response period within 95 days | |
| Topic | Health: Risk of hot flashes in midlife women, pregnancy history, hormonal contraceptive use, menstrual history | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Yes | A ‐ Adequate |
Whitmore 1976.
| Methods | Random allocation: method not specified | |
| Data | Individuals who had purchased a new car | |
| Comparisons | 1. Key ring incentive with questionnaire
2. No incentive Follow up sent at 2 weeks |
|
| Outcomes | — | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Willits 1995.
| Methods | Random allocation: method not specified | |
| Data | Residents of Pennsylvania (US) | |
| Comparisons | 1. No pre‐amble; General question first
2. No pre‐amble; General question last
3. Pre‐amble; General first
4. Pre‐amble; General last Follow up sent to non‐respondents (postcard and 2 additional mailings including another copy of the questionnaire) |
|
| Outcomes | — | |
| Topic | Health: Quality of life (QoL) in rural areas, QoL in relation to community spirit, health care services, recreational opportunities, job opportunities, air quality | |
| Mode of Administration | Postal | |
| Notes | Mean age: 42.6 years; Mainly males | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Windsor 1992.
| Methods | Random allocation: method not specified | |
| Data | Individuals listed on electoral registers | |
| Comparisons | 1. Questionnaire included questions on ethnic origin and housing tenure
2. Questionnaire included question on housing tenure only
3. Questionnaire included question on ethnic origin only
4. Neither question included 2 reminders sent |
|
| Outcomes | Response period not specified | |
| Topic | Health: Health and hospital survey ‐ health and hospital attendance, consultation with GPs, demographics, housing tenure | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wiseman 1972.
| Methods | Random allocation: systematic allocation | |
| Data | Residents of a suburban Boston community, USA | |
| Comparisons | 1. Telephone pre‐notification ‐ mail survey 2. No pre‐notification ‐ mail survey | |
| Outcomes | Response period not specified | |
| Topic | Health: Birth control devices, legalising abortions, lowering the legal drinking age Non‐health: Giving state aid to catholic schools |
|
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wiseman 1973.
| Methods | Random allocation: systematic allocation | |
| Data | Residents in a statewide telephone listings, Massachusetts, USA | |
| Comparisons | 1. 10 cent incentive (MI); Postcard follow up 3 days after initial mailing (FU); Business reply envelope (BRE); Offer of survey results (OR) 2. MI; No follow up (No FU); BRE; OR 3. MI; FU; BRE; No offer of survey results (No OR) 4. MI; No FU; BRE; No OR 5. MI; FU; Stamped return envelope (SRE); OR 6. MI; No FU; SRE; OR 7. MI; FU; SRE; No OR 8. MI; No FU; SRE; No OR 9. No monetary incentive (NI); FU; BRE; OR 10. NI; No FU; BRE; OR 11. NI; FU; BRE; No OR 12. NI; No FU; BRE; No OR 13. NI; FU; SRE; OR 14. NI; No FU; SRE; OR 15. NI; FU; SRE; No OR 16. NI; No FU; SRE; No OR | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Attitudes and opinions about Massachusetts state lottery | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Woodward 1985.
| Methods | Random allocation: alternation | |
| Data | Household members (South Australia) | |
| Comparisons | 1. Cover letter included offer of chance to win free dinner
2. Cover letter did not include offer Follow up at 1, 3 and 7 weeks |
|
| Outcomes | Response within 10 weeks | |
| Topic | Health: Respiratory history of the youngest child | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Worthen 1985a.
| Methods | Random allocation: method not specified | |
| Data | School teachers listed on the Education Association Membership roster (Utah, US) | |
| Comparisons | 1. Personalised cover letter 2. Form cover letter | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Classroom teachers opinion about what should be taught in educational measurement course | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Worthen 1985b.
| Methods | Random allocation: method not specified | |
| Data | School teachers listed on the Education Association Membership roster (Utah, US) who did not respond to an earlier questionnaire with a personalised letter | |
| Comparisons | 1. Personalised cover letter 2. Form cover letter | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Classroom teachers opinion about what should be taught in educational measurement course | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Worthen 1985c.
| Methods | Random allocation: method not specified | |
| Data | School teachers listed on the Education Association Membership roster (Utah, US) who did not respond to an earlier questionnaire with a standard form letter | |
| Comparisons | 1. Personalised cover letter 2. Form cover letter | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Classroom teachers opinion about what should be taught in educational measurement course | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wotruba 1966.
| Methods | Random allocation: systematic division of a random sample | |
| Data | Urban household residents | |
| Comparisons | 1. 25 cents sent with questionnaire 2. 50 cents promised on return of questionnaire 3. No incentive | |
| Outcomes | Response within 6 weeks | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Wright 1984.
| Methods | Random allocation: alternation | |
| Data | People listed in the latest telephone directories, New Zealand 1983 | |
| Comparisons | 1. Personal salutation (P); Black and white letterhead (BW); White outward envelope (Wh); $100 cash lottery incentive (Ca) 2. P; BW; Wh; Garden voucher lottery incentive (Ga) 3. P; BW; Brown outward envelope (Br); Ca 4. P; BW; Br; Ga 5. P; Coloured letterhead (Co); Wh; Ca 6. P; Co; Wh; Ga 7. P; Co; Br; Ca 8. P; Co; Br; Ga 9. Impersonal salutation (IP); BW; Wh; Ca 10. IP; BW; Wh; Ga 11. IP; BW; Br; Ca 12. IP; BW; Br; Ga 13. IP; Co; Wh; Ca 14. IP; Co; Wh; Ga 15. IP; Co; Br; Ca 16. IP; Co; Br; Ga | |
| Outcomes | Response period not specified | |
| Topic | Non‐health: Motivation of gardeners and users of garden products, socio‐demographics | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Wright 1995.
| Methods | Random allocation: systematic sample from list ordered alphabetically | |
| Data | New Zealand councillors who had participated in another survey 18 months previously | |
| Comparisons | 1. Pre‐notification letter sent 2 weeks prior to questionnaire mailing 2. No pre‐contact | |
| Outcomes | Response after 2 follow‐up reminders | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Wunder 1988.
| Methods | Random allocation: alternation | |
| Data | Subscribers to a large health maintenance organisation in a major metropolitan area in the Midwestern United States | |
| Comparisons | 1. Hand addressed envelope 2. Computer generated address on envelope | |
| Outcomes | Response period not specified | |
| Topic | Health: Satisfaction benefit package, characteristics of subscribers | |
| Mode of Administration | Postal | |
| Notes | Method of allocation ascertained through contact with author | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Wynn 1985.
| Methods | Random allocation: alternation | |
| Data | Members, past and present, of an exercise and recreational club in a medium‐sized south‐western city (US) | |
| Comparisons | 1. No pre‐contact by telephone 2. Telephone pre‐contact asking permission to send questionnaire (foot‐in‐the‐door manipulation) 3. Telephone pre‐contact asking questions (probe‐foot‐in‐the‐door manipulation) | |
| Outcomes | Response period not specified | |
| Topic | Health: Planning of a possible expansion effort for an exercise recreational club | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | No | C ‐ Inadequate |
Zusman 1987.
| Methods | Random allocation: on the basis of study identification number and done without reference to subject characteristics | |
| Data | Undergraduate transfer students | |
| Comparisons | 1. $1 incentive sent with first mailing
2. No incentive sent Follow up of non‐respondents several weeks after first mailing |
|
| Outcomes | Response period not specified | |
| Topic | Not specified | |
| Mode of Administration | Postal | |
| Notes | — | |
| Risk of bias | ||
| Item | Authors' judgement | Description |
| Allocation concealment? | Unclear | B ‐ Unclear |
Characteristics of excluded studies [ordered by study ID]
| Study | Reason for exclusion |
|---|---|
| Allen 1980 | The comparison in this study is biased by the fact that people in the pre‐notification group are given the choice of whether to receive the questionnaire or not whereas people in the no pre‐notification group are not given this choice. |
| Anderson 1975 | It was not possible to determine whether this study was randomised. |
| Angus 2003 | Not a randomised controlled trial. |
| Armstrong 1975 | Review article. |
| Asch 1994 | The comparison in this study is confounded ‐ the author, with reference to the several differences between the 2 mailing strategies, states 'We cannot determine which of these differences underlies our results.' |
| Ash 1952 | It was not possible to determine whether this study was randomised. Attempts to contact the author have been unsuccessful. |
| Baron 2001 | The comparison in this study is confounded by colour of the questionnaire. |
| Bevis 1948 | It was not possible to determine whether this study was randomised. |
| Biggar 1992 | All comparisons in the study are confounded. |
| Blumberg 1974 | It was not possible to determine whether this study was randomised and the data which would be needed is only referred to not presented. Attempts to contact author have been unsuccessful. |
| Blumenfeld 1973 | It was not going to be possible to determine whether this study was randomised as the author has died. |
| Brechner 1976 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Brennan 1958 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Brennan 1990 | The comparison in this study is confounded. |
| Cartwright 1968 | The comparison of different lengths is confounded by other differences between the two questionnaires. |
| Cartwright 1989 | It was not possible to determine whether this study was randomised. Contact details of the author is unavailable. |
| Champion 1969 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Childs 2005 | The study did not calculate the response for the different order of administration of the questionnaires. |
| Cook 1985 | Incentive only given after agreement to participate in a further study, not just for returning the questionnaire. |
| Dillman 1972 | No useful experimental data presented. |
| Dunlap 1950 | It is not possible to determine whether this study was testing return rate of a questionnaire. Attempts to contact author have been unsuccessful. |
| Eisinger 1974 | It was not possible to determine whether this study was randomised. Attempts to contact authors have been unsuccessful. |
| Elinson 1950 | There is insufficient data presented in this paper to include it. It has also not been possible to determine whether the questionnaire in the experiment is postal. Attempts to contact authors have been unsuccessful. |
| Everett 1997 | The comparison in this study is confounded by colour of the questionnaire. |
| Fang 2006 | This study did not calculate the response but inspected the correlation between the material incentive and the participants characteristics. |
| Ferriss 1951 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Furse 1981 | Authors cannot remember whether the study was randomised. |
| Gerace 1995 | This study examines response rates of a postal request for more information not a questionnaire. |
| Gillespie 1975 | The comparison in this study is confounded. |
| Hansen 2004 | Not a randomised controlled trial. |
| Hare 1998 | The comparison in this study is confounded by colour of the questionnaire. |
| Harlow 1993 | Examines response rates to telephone interviews not postal questionnaires. |
| Haugejorden 1987 | Randomised controlled trial but not of methods to increase response to postal questionnaires. |
| Hawes 1987 | Author no longer has original data to be able to provide confirmation of numbers of questionnaires administered and returned. |
| Heads 1966 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Heje 2006 | The primary questionnaire was delivered personally to the patient either at the surgery or at home. |
| Helgeson 2002 | Author no longer has original data to be able to provide confirmation of numbers of questionnaires administered and returned. |
| Hing 2005 | Not a postal questionnaire. |
| Hinrichs 1975 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Hughes 1989 | Author was contacted: the study records have been discarded. |
| Ives 1990 | Author was contacted: confirmed that participants were not randomly allocated. |
| Jiang 2005 | Not a randomised controlled trial. |
| Kerin 1974 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Kerin 1977 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Kerin 1983 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Kimball 1961 | It was not possible to confirm that this study was randomised. Attempts to contact author have been unsuccessful. |
| Larsson 1970 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Longworth 1953 | Author drew six different samples, and tested a different type of intervention on each without a comparison group. |
| Lopez‐ Cano 2007 | Not a randomised controlled trial. |
| Lund 1988 | Comparisons of questionnaires which were mailed are confounded. |
| Marks 1981 | Author cannot remember whether the study was randomised. |
| May 1960 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| McDermott 2003 | Incentives were same for all the three questionnaires. |
| Mehta 1995 | Two groups received postal questionnaires, but one group received a combination of methods (monetary incentive, pre‐notification and follow‐up). Comparisons for combinations of methods have not been created in this review. |
| Nitecki 1975 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Oden 1999 | The comparison in this study is confounded by colour of questionnaire. |
| Perneger 2003 | The intervention did not include strategies to increase response to a postal or electronic questionnaire. |
| Peytremann‐Bridevaux 2006a | The intervention did not include strategies to increase response to a postal or electronic questionnaire. |
| Porter 2004 | The data presented in this paper are the same as that presented in an earlier paper Porter 2003. |
| Pottick 1991 | This study examines postal methods to improve response to a face to face survey. |
| Robin 1973 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Robin 1976 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Roeher 1963 | It is not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Rudd 1980 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Salomone 1978 | The number of people allocated to each experimental group is not presented and attempts to obtain this information from the authors have been unsuccessful. |
| Senf 1987 | Option to refuse postcards were sent to half of all participants prior to sending questionnaire. However, response rates to questionnaires could not be compared because questionnaires were returned anonymously. |
| Shackleton 1982 | The data presented in this paper are the same as that presented in an earlier paper by Shackleton (1980). |
| Shermis 1982 | Comparisons of questionnaires which were mailed are confounded. |
| Sheth 1975 | The data presented in this paper are from the same study as those presented in an included study by Roscoe and Sheth (1975). |
| Sirken 1960 | Could not confirm random allocation. Author contacted: stated only that "this was not a clinical trial." |
| Smith 1972 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Smith 1977 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Smith 1987 | It was not possible to determine how many participants were allocated to each experimental group and attempts to obtain this information from the authors have been unsuccessful. |
| Snyder 1984 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Suhre 1989 | Analyses by means of logit analysis and no useable outcome data were available. Author contacted: no useable data obtained. |
| Sullivan 1995 | Comparison groups do not meet 'postal questionnaire' criteria. |
| Sutherland 1996 | There are too many differences between the two groups to be able to compare any of these differences without confounding. |
| Tan 1997 | Review article. |
| Trice 1985 | Not a postal questionnaire. |
| Walker 1977 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Ward 1994 | All comparisons in the study are confounded. |
| Watson 1965 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Weiss 1985 | It was not possible to determine whether this study was randomised. Attempts to contact author have been unsuccessful. |
| Weissenburger 1987 | It was not possible to determine whether this study was randomised. Contact details of the author is unavailable. |
| Wildman 1977 | The comparison in this study is confounded by paper quality. |
| Zagumny 1996 | Not a postal questionnaire. |
| Zwisler 2004 | Review article. |
Contributions of authors
Mike Clarke, Carolyn DiGuiseppi, Phil Edwards and Ian Roberts contributed to study design, record screening, reviewing reports, data extraction and drafting of the report. Phil Edwards and Ian Roberts analysed the data. Sarah Pratap and Irene Kwan contributed to data searches and data extraction. Reinhard Wentz conducted all electronic searches. Phil Edwards and Rachel Cooper contributed to record screening, reviewing reports, data extraction, additional data analysis and alterations to the report during the 2003 update. Phil Edwards and Lambert Felix contributed to record screening, reviewing reports, data extraction, additional data analysis and alterations to the report during the 2008 update.
Sources of support
Internal sources
No sources of support supplied
External sources
The BUPA Foundation, UK.
The Nuffield Trust, UK.
Declarations of interest
None.
Unchanged
References
References to studies included in this review
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