Gender balance, representativeness, and statistical power in sexuality research using undergraduate student samples

It is well-documented thatagreatdealofpsychological research, including the study of sexual behavior, relies on undergraduate students for its study participants (e.g., Landrum & Chastain, 1999; Miller, 1981; Owen, Rhoades, Stanley, & Fincham, 2010; Saks & Seiber, 1989). In many ways, undergraduate students are an ideal sample for understanding sexual behavior as this is developmentally consistent for young adults. Beyond providing an inexpensive and readily available source of research subjects, the use of student pools has also been justified by the educational benefits it provides to students who participate, such as increased knowledge about contemporary psychology and research ethics (Rosell et al., 2005). However, there are also a couple of central concerns with the use of undergraduate student participants, namely gender imbalances and the representativeness of the samples. Researchers are often concerned with obtaining balanced samples, equallyor nearly equally-sized subgroups. Although such a concern is well-rooted in statistical theory, it can pose practical limitations for those who rely largely on undergraduate student samples, as undergraduates are often given the opportunity to self-select into particular research studies (Miller, 1981). Undergraduate researchpoolscanbeoverrepresentedbywomen, freshman, and psychology majors (Barlow & Cromer, 2006), and gender, prior sexual experience, and sexual attitudes may be related to the types of studies in which students are willing to participate (Gaither, Meier, & Sellbom, 2003; Wiederman, 1999). Specific concerns have been raised regarding the imbalancebetweenthenumberofmenandwomenparticipating insexuality research, particularly a general overrepresentation of women (McCray, King, & Bailly, 2005) or women’s willingness to volunteer (Rosenbaum, 1997). Other research, however, has pointedout thatmenmayvolunteermorefrequentlyforparticular types of studies, such as those involving the viewing of images of heterosexual activity (Gaither et al., 2003). Gender imbalance should be understood through representativeness and statistical power. As an example, consider a study conducted at a small college of 1,000 students in which the distribution of gender groups at the college is quite imbalanced (e.g., 80% female and 20% male). Given that females may be more inclined to agree to participate in our research, we could easilyendupwithasampleof100studentscontaining85females and 15 males. Our resulting sample is clearly not balanced, but it may well be representative in that it approximates the distribution of gender groups of the college. Because a sample size of men (n = 15) in one group is likely too small to test differences between men and women, we could increase the number of male participants (i.e., collect data from 70 more males while not collecting data from additional females). Although this might be useful toaddress the researchquestions, itmaycomeat thecostof representativeness. That is, we will have 10.6% of all the women and 42.5% of all the men from this population (students at this college). Additionally, there are practical considerations regarding the time and expense required for additional data collection to achieve gender balance in samples. Theaimofmuchofsocial researchis tomakeobservations ina research setting that reflects what would be observed among different people, in different settings, under different treatment conditions, and using alternative measurements (Shadish, Cook, & Campbell, 2002). We increase confidence that this expectation has been met by collecting data from people with a wide range of characteristics and/or by measuring constructs in slightly different ways. Researchers of human sexuality often are interested in sexual attitudes, beliefs, and behaviors that exist beyond the college campus. Though a single study based on a sample of undergraduate students from a particular college is likely not repreE. R. Dickinson (&) J. L. Adelson J. Owen College of Education and Human Development, University of Louisville, Louisville, KY 40292, USA e-mail: emily.dickinson@louisville.edu