Table 2.
Descriptive statistics of the sample by study round.
| Round 1 (n = 1489) |
Round 2 (n = 1499) |
Total (n = 2988) |
|
|---|---|---|---|
| Mean | Mean | Mean | |
| Returned kit within 30 days | 71.3 | 70.8 | 71.0 |
| Incentive structure | |||
| Control | 16.8 | 20.0 | 18.4 |
| GBP 5 voucher | 16.5 | 20.2 | 18.4 |
| GBP 10 voucher | – | 20.1 | 10.1 |
| Lottery EV GBP 5 | 16.6 | – | 8.3 |
| Choice EV GBP 5 | 16.6 | – | 8.3 |
| Choice EV GBP 10 | – | 20.3 | 10.2 |
| GBP 5 endowment | 16.8 | – | 8.4 |
| GBP 10 endowment | – | 19.3 | 9.7 |
| GBP 5 charity | 16.7 | – | 8.3 |
| Gender | |||
| Male | 32.6 | 34.7 | 33.7 |
| Level of poverty/deprivation | |||
| Index of Multiple Deprivation (IMD) Scoreb | 20.4 (14.34) | 20.0 (13.92) | 20.2 (14.13) |
| Age | |||
| 16–19 years | 33.0 | 28.4 | 30.7a |
| 20–24 years | 66.3 | 66.6 | 66.4 |
| Age missing | 0.7 | 5.0 | 2.9a |
| Ethnicity | |||
| White | 88.4 | 84.6 | 86.5a |
| Black | 1.05 | 1.3 | 1.4 |
| Asian | 1.7 | 0.9 | 1.3 |
| Other race | 0.3 | 0.3 | 0.3 |
| Mixed ethnicity | 3.1 | 3.1 | 3.1 |
| Unknown | 4.9 | 9.7 | 7.3a |
| New partner in the last 3 months | |||
| Yes | 62.8 | 60.4 | 61.6 |
| No | 26.8 | 23.7 | 25.3 |
| Unknown | 10.4 | 15.9 | 13.2a |
| Two or more sexual partners in last 12 months | |||
| Yes | 68.2 | 63.0 | 65.6a |
| No | 22.0 | 21.3 | 21.7 |
| Unknown | 9.80 | 15.6 | 12.7a |
| Chlamydia test in the last 12 months | |||
| Yes, positive test | 33.4 | 33.0 | 33.2 |
| Yes, negative test | 8.30 | 7.5 | 7.9 |
| No | 48.8 | 46.3 | 47.6 |
| Unknown | 9.50 | 13.2 | 11.4a |
| Condom use when last had sex | |||
| Yes | 16.9 | 16.3 | 16.6 |
| No | 71.5 | 67.9 | 69.7a |
| Unknown | 11.6 | 15.7 | 13.7a |
Notes: A response of ‘unknown’ means that the respondent was asked the question but responded ‘ I'd rather not say’ in the online questionnaire when requesting his/her kit or requested their test kit via text message and therefore did not have the opportunity to fill in the online questionnaire.
‘Age missing’ includes 8 participants who were either over the age of 24 or gave an inaccurate age figure (e.g. 100, 111). They would not have been eligible for NCSP testing and therefore were denoted as ‘age missing’ along with those who requested their kit by text and did not report an age.
Statistically significant difference (at the 95% level) in means between characteristics of sample in Round 1 and Round 2.
Figure in parenthesis is standard deviation.