VARIATIONS IN RECRUITMENT YIELD, COSTS, SPEED AND PARTICIPANT DIVERSITY ACROSS INTERNET PLATFORMS IN A GLOBAL STUDY...

For a world-wide, Internet-based study on HIV/AIDS and HIV testing knowledge, we compared the yields, speed and costs of recruitment and participant diversity across free postings on 13 Internet or social media platforms, paid advertising or postings on 3 platforms, and separate free postings and paid advertisements on Facebook. Platforms were compared by study completions (yield), time to completion, completion to enrollment ratios (CERs), and costs/ completion; and by participants' demographic characteristics, HIV testing history, and health literacy levels. Of the 482 English-speaking participants, Amazon Mechanical Turk yielded the most participants, recruited participants at the fastest rate and had the highest CER (0.78) and lowest costs / completion. Of the 335 Spanish-speaking participants, Facebook yielded the most participants and recruited participants at the fastest rate, although Amazon Mechanical Turk had the highest CER (0.72) and lowest costs/completion. Across platforms participants differed substantially according to their demographic characteristics, HIV testing history and health literay skills. The study results highlight the need for researchers to strongly consider choice of Internet or social media plaforms when conducting Internet-based research. Because of the sample specifications and cost restraints of studies, specific Internet/ social media or participant selection plaforms will be much more effective or appropriate than others.