When designing recruitment materials researchers should consider the study, setting, cultural and age-based needs of the population, (or population vulnerability). Below are the most commonly used subject recruitment methods for research purposes. This includes both social-behavioral and biomedical recruitment strategies:
- Direct recruitment includes physicians talking with their own patients about the study, contact between the study team and potential subjects in person, on the phone or on the Internet. This also includes contact between teachers and their own students. Researchers should take considerable care to avoid pressuring the person to participate in the study.
- Convenience samples are typically easy to recruit because researchers recruit subjects that are readily available rather than selecting from the entire population. An example of a convenience sample may include recruiting from one’s own institution or social network.
- Advertisements, flyers, information sheets, notices, Internet postings and/or media are used to recruit subjects. IRB reviewers will approve the text of these recruitment means before they are actually posted.
- Recruitment letters sent to site officials (e.g., executive directors or school principals). Researchers should provide contact information so interested parties can contact them. Upon further contact, the researcher and potential subject can engage in a deeper conversation about the study parameters. However, in some large-scale, low risk studies, it might be acceptable to ask the person to opt out if they are not interested. Recruitment letters are brief and include information about how the person was selected to receive the letter (e.g., “you are invited to participate in this study because you are a third year math teacher”), what the study involves, an overview of any risks or potential benefits, and the researchers contact information.
- Random or probability sampling includes snowball sampling (i.e., chain sampling, referral sampling), random digit dialing, or other methods of referral used primarily in the social and behavioral sciences. Non-investigator referrals can include teachers, healthcare providers, social workers, or other professionals. Researchers may provide information letters to colleagues or associates asking that they distribute the sheets to people within their network. Researchers should be aware that non-investigators who are not health care providers are prohibited from accessing personal health information.
- Recruitment databases include research participants who have given permission for future contact. Researchers should contact these individuals and gauge if they meet the inclusion criteria if the study protocol. In many case, prospective participants gave permission to be contacted for future studies by means of check-off box in a consent form for a previous study. Sites like ResearchMatch.org and Amazon Mechanical Turk (MTurk) offer researchers an opportunity to engage with potential participants.
Above all, a researcher should consider multiple options when recruiting subjects and which approach best suits their population of interest.