Quantifying Time and Effort Spent on Recruiting Participants

Recruiting participants for your study and experiment can be expensive, but it can be even more costly if you don’t know whether your recruitment drives are successful. Sending a Research Assistant to poster a campus may sound good (and cheap) in theory, but how much is his time actually costing you and, more importantly, what kind of return is it bringing you on your investment (ROI)?

In one academic study on research recruitment at a chiropractic research college, unforeseen difficulties arose in acquiring the 48 student volunteers needed to complete the project. The researchers used various methods of recruitment and quantified the ROI. For example, having a research assistant put up posters, signs, flyers, and sign-up sheets around campus for over 1 year brought only 13 eligible participants to the study. Direct engagements through class presentations (40 minutes) and research booths (4 hours) brought another 34 participants. However these participants were local students, in the professor’s classes, and received course credit for participation. This cast doubt on whether or not these students truly participated out of “free will”.

As the U.S. Department of Human and Health Services noted: “Participant recruitment is a major challenge in many research studies involving human subjects … Findings from several studies suggest that recruitment often takes longer than anticipated, projects incur higher costs than expected, and scientists routinely overestimate the number of participants available for enrollment in their studies. Even in studies that succeed in recruiting large numbers of patients, participation rates are low; only 3-20% of the eligible participant pool chooses to participate. A survey of research studies found that 34% of recruiters recruited less than 75% of their planned sample, and this reduction in the sample size leads to reductions in the statistical power of the study.” A Wall Street Journal article from April 2016 elaborated on this even more clearly: “About 40% of clinical trials don’t recruit enough patients to meet their goals”.

A recent PubMed research paper on clinical trials conducted an in-depth analysis of ROI and found that “Poster advertising, web-based advertising, and mental health worker referrals were the cheapest methods per randomized participant; however, the ratio of randomized participants to initial contacts differed markedly per source. Advertising online, via posters, and on a local radio station were the most cost-effective recruitment methods for soliciting participants who subsequently were randomized into the trial”.

Your ROI will differ depending on your study type. Harder to recruit for demographics will require much more targeted efforts, which may include one or more advertising channels and careful tracking of which channel is actually yielding results. Longer studies, which often require repeat visits to a lab or having the participant do something at home, require careful participant management and consistent interaction with participants. Further, participants must be carefully screened to ensure they fit the study. An interested participant who saw an ad for a “Depression study for males” on the bus is likely to have missed that he must be over 40 and have no liver problems. Every participant that you have to pre-screen manually takes important time away from your lab and decreases your recruitment ROI.


Research And Me has pioneered a novel way of allowing you to track your ROI, provide participant screening, and target recruitment to the required demographics – all in one place. We believe that researcher time saved is recruitment well done.

Quantifying Time and Effort Spent on Recruiting Participants

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