200. Selection of Research Participants

Updated July 1 2019

IRBs are required to make a specific determination that the selection of participants for a research project is equitable (45 CFR 46.111 item (a)(3)). In making this determination, the IRB will consider the scientific design, susceptibility to risk, likelihood of benefit, practicability, and fairness.

The IRB must also confirm that risks to participants are reasonable in relation to anticipated benefits (§45.111 item (a)(2)). In making this determination, the IRB evaluates the number of participants the investigator expects to enroll with consideration for procedures for data collection and analysis. Therefore, increasing (or decreasing) the expected number of enrolled participants constitutes a change to an approved protocol. As with any other protocol change, researchers wishing to enroll more or fewer participants than noted in the application must obtain prior IRB approval for a protocol amendment.

Selection of Research Participants

Research populations should be selected for reasons related to the problem being studied. Use of appropriate populations helps to ensure a fair distribution of the burdens and benefits of research (based on the principle of Justice in the Belmont Report).

Those who are already burdened (e.g., by disabilities, low socio-economic status) should not be asked to accept the burdens of research unless the research is relevant to their condition or circumstances, or if other appropriate participants cannot be found. Investigators and IRBs must also be careful not to overprotect populations to the extent these are consistently excluded from participating in research. While the inclusion of disproportionate numbers of institutionalized persons, or racial or ethnic minorities in research studies might overburden these groups relative to the anticipated benefits of the research, underrepresentation assures they will not benefit from the research.

The IRB gives special consideration to protecting the welfare of subjects that are vulnerable to coercion or undue influence such as children, prisoners, individuals with impaired decision-making capacity, or economically or educationally disadvantaged persons. The IRB also recognizes that additional populations such as students may qualify as vulnerable populations and need safeguards in place for their protection during study participation.

The IRB reviews proposed research to determine whether the study protocol includes enrollment of vulnerable subjects and whether appropriate safeguards are in place. When some or all of the participants are likely to be vulnerable, the IRB should ensure that additional safeguards are included in the research design to protect the rights and welfare of these participants. As applicable, the IRB considers the following elements when reviewing research involving vulnerable subjects:

  • Inclusion/exclusion criteria;
  • Over-selection or exclusion of certain groups based on perceived limitations (i.e., targeting prisoners as research subjects because they are a readily available "captive" population);
  • Knowledge of applicable or local laws that bear on the decision-making process (i.e., emancipated individuals, legally authorized representatives, age of majority for research consent).


Social justice dictates there be an order of preference in the selection of classes of participants:

  1. adults before children,
  2. competent individuals before incompetent individuals, and
  3. non-institutionalized persons before institutionalized persons.

The IRB follows applicable federal and state regulations and IRB policy to assist in reviewing and approving proposed research that involves vulnerable subjects such as:

  • Pregnant Women, Human Fetuses and Neonates (45 CFR 46, Subpart B)
  • Research Involving Prisoners (45 CFR 46, Subpart C)
  • Research Involving Children (45 CFR 46, Subpart D, 21 CFR 50, Subpart D, U.S. Department of Education, Subpart D, and OHRP Guidance on Special Protections for Children as Research Subjects)
  • Research Involving Individuals with Impaired Consent Capacity
  • Research involving university students
  • Research involving K-12 students

Convenience Sampling

Students, employees, and institutionalized, or economically or educationally disadvantaged persons should not be selected on the basis of convenience (i.e., participants are readily available) when not otherwise appropriate for inclusion in the research study.

Reliance on populations of convenience is generally prohibited but may be acceptable when

  1. the risk posed by the research is no more than minimal;
  2. adequate steps have been taken to minimize potential undue influence during recruitment and consent;
  3. the harms that may arise in the research would not be exacerbated by the ease of availability of the population; and
  4. investigators do not generalize the results beyond the research populations.

Use of Student Subject and Online Participant Pools

University students and students enrolled in other institutions within the Nevada System of Higher Education (e.g., TMCC ) may be offered the opportunity to participate in research for credit as part of a course requirement via the University Department of Psychology SONA Subject Pool or the Undergraduate Research Pool (for students enrolled in humanities, social, managerial and behavioral sciences). NOTE: Documentation of site permission is required to enroll students from other institutions, including those within NSHE.

When students in subject pools constitute the research population, the research must conform to the requirements of both the subject pool and the IRB.

Recruiting from established groups of individuals who are willing to participate in research, including online pools of paid participants and student subject pools, may enhance recruitment efforts but may limit the generalizability of results.

Individuals recruited from participant groups must be free to decline to participate or withdraw from participation at any point without penalty. Parental permission and youth assent are required to enroll participants who meet the regulatory definition of children.

IRB Assessment of Equity in Participant Selection

The IRBs evaluate inclusion/exclusion criteria with consideration for research design and participant risk. Adequate representation of women, minorities, or other underrepresented groups is particularly important in studies of diseases, disorders, and conditions that disproportionately affect these populations. When appropriate, the IRBs will ensure such populations are adequately represented so that the research findings will be meaningful for these groups.

The IRBs consider the researchers' evaluations of potentially vulnerable populations to determine if any subgroups within the research population might be more susceptible to the risks presented by the study, and assess safeguards to determine if the risk susceptibility has been sufficiently addressed.

The IRBs review recruitment methods, locations, and materials to

  • encourage recruitment of a broad cross-section of research participants, and
  • ensure safeguards are in place to minimize pressures on prospective participants to enroll in a research study.

The IRBs evaluate the risks and inconveniences associated with research procedures with consideration for research benefits, with the understanding that the populations subject to the risks and burdens of being research participants should be among those most likely to benefit from the research.