Table 2.

Summary of studies—Intervention, results, and retention.

Authors (year)	Intervention	Intervention duration	Results by recruitment method	Retention methods	Retention or completion rates
Batterham (2014)	Online survey	Time taken to complete online survey	Online surveys cost less than postal surveys- Internal links more cost less than external links. Content of ads crucial to the cost aspect of online recruitment. Terms “mental health problems” was more effective than “emotional well-being.”	Completion rate percentage calculated in order to see how many people completed surveys after responding to ads.	Survey: 10.4% completion for Problem/Altruistic ad; 11% completion for Problem/Self-Gain ad; 5.8% completion for Positive/Altruistic ad; 9% completion for Positive/Self-Gain ad
Fenner (2012)	Health survey	15-30 minutes to complete survey, either electronically or at the site	Facebook recruitment found to compare favorably with traditional recruitment methods. Facebook also found to yield a representative sample	Calculated a participation rate for those who completed the survey out of those who clicked on the ad	Survey: 3.5% participation rate out of all who clicked on ad, 65% survey completion of those who consented
Frandsen, Walters, & Ferguson (2013)	[To be reported in future publication]	[To be reported in future publication]	Most participants recruited through online methods (Facebook), Facebook cost twice as much per participant than print media. Participant demographics from each method of recruitment were equally matched meaning online methods can supplement traditional methods.	Not reported	Not reported
Graham, Bock, Cobb, Niaura, & Abrams (2006)	Telephone counseling or using QuitNet.com (an Internet smoking cessation website)	N/A	Google yielded the greatest number of participants	Completing baseline assessment	51.3% completed baseline assessment and were randomized to treatment
Graham, Milner, Saul, & Pfaff (2008)	Telephone counseling and using QuitNet.com for smoking cessation treatment	[Not reported]	Traditional methods yielded more participants and found those participants engaged with the website more, online methods reached typically hard-to-reach populations and was found to cost less	Number of logins, minutes per login, number of page views, and interactions with other users and counselors	18.4% of identifiers on QuitNet were from traditional media, 81.6% from online media. 9.1% of online clicks registered for cessation treatment (6.8% Web-only, 1.1% phone only, 1.2% both); retention data not available at time of analysis
Heffner, Wyszynski Comstock, Mercer, & Bricker (2013)	Baseline survey, 3-month follow-up assessment	Time taken to complete baseline survey and follow-up 3 months later	GoogleAds had highest participant yield, social media and GoogleAds cost more than traditional methods. No difference between traditional and online methods in data retention or intervention success	Completing follow-up after 3 months went by	3-month retention: Overall: 52%, Standard media: 53%, email: 46%, word of mouth: 62%, medical Internet: 56%, social media: 64%, Google: 46%
Morgan, Jorm, & Mackinson (2013)	Patient Health Questionnaire, receiving weekly emails with self-help strategies	6 weeks	Google had highest participant yield, found to be less time-consuming and more effective than other recruitment techniques, even those that are free.	Completing baseline survey, receiving emails, and completing depression questionnaire	Survey: 78% completion after consent
Ramo, Hall, & Prochaska (2010)	10-item smoking questionnaire; Fagerstron Test of Nicotine Dependence; smoking stages of change questionnaire	20 min survey	Adbrite Internet advertisements resulted in highest participant yield (Facebook was most successful Internet Web sites), craigslist and SSI were more successful at targeting young adult smokers	Completing survey in entirety (all questionnaires)	Survey: 59.8% completion after eligibility screening
Ramo & Prochaska (2012)	Smoking Stages of Change Questionnaire, A Smoking Questionnaire, Thoughts about Abstinence form	Time to complete survey	Facebook found to be more affordable than other previously- used methods with a similar population (Internet marketing company cost-per-participant=$42.77), success of specific ads dependent upon Facebook’s approval of the ad	Completing survey in entirety	Survey: 50% completion after eligibility screening
Ramo, Rodriguez, Chavez, Sommer, & Prochaska (2014)	Smoking History Questionnaire, Smoking States of Change scale, baseline survey, Private Facebook group tailored to their readiness to quit (ready, thinking about it, not ready), bioconfirmation of nonsmoking tests	One year	Facebook found to be efficient and affordable. Newsfeed ads more successful—Ads with simple pictures of cigarettes, the study logo, and general info messaging were most successful	Participate in a Facebook group and complete follow-up assessments with saliva cotinine tests at 3, 6, and 12 months.	34% of those who were eligible and consented completed the intervention
Raviotta, Nowalk, Lin, Huang, & Zimmerman (2014)	Complete baseline survey and postvaccination survey. Half participants randomized to standard dosing group (0, 2, & 6 months) and half randomized to alternate dosing group (0, 2, & 12 months).	[Not reported]	Traditional methods reached more people, but online methods were more likely to reach hard-to-reach populations. Direct cost was higher for electronic advertising	Completing four visits to study site for intake survey, blood draw, vaccination does 1, 2, & 3, and final blood draw and survey	Survey: 70.7% completion after eligibility screening
Valdez, Guterbock, Thompson, Reilly, Menefee, Bennici, Williams, & Rexrode (2014)	Survey	Time taken to complete the survey	Facebook found to be affordable, but not feasible for large, quantitative studies	Completing the survey in its entirety	Survey: 77.2% completion after eligibility screening