The following is a modified excerpt from Applied Qualitative Research Design: A Total Quality Framework Approach (Roller & Lavrakas, 2015, pp. 107-109).
Fundamental to the design of a focus group study is group composition. Specifically, the researcher must determine the degree of homogeneity or heterogeneity that should be represented by the group participants. As shown below, there are many questions the researcher needs to contemplate, such as the extent of similarity or dissimilarity in participants’ demographic characteristics, as well as in their experiences and involvement with the subject matter.
| Questions When Considering Heterogeneity vs. Homogeneity |
A few of the questions the focus group researcher might consider when determining the desired heterogeneity or homogeneity among group participants include:
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Whether or not—or the degree to which—group participants should be homogeneous in some or all characteristics has been at the center of debate for some years. On the one hand, Grønkjær, Curtis, Crespigny, and Delmar (2011) claim that at least some “homogeneity in focus group construction is considered essential for group interaction and dynamics” (p. 23)—for example, participants belonging to the same age group may have similar frames of reference and feel comfortable sharing their thoughts with people who have lived through the same experience. In the same vein, Sim (1998) states that, “the more homogeneous the membership of the group, in terms of social background, level of education, knowledge, and experience, the more confident individual group members are likely to be in voicing their [own] views” (p. 348). Even among strangers, there is a certain amount of comfort and safety in the group environment when the participants share key demographic characteristics, cultural backgrounds, and/or relevant experience.
A problem arises, however, if this comfortable, safe environment breeds a single-mindedness (or “groupthink”) that, without the tactics of a skillful moderator, can stifle divergent thinking and result in erroneous, one-sided data. Heterogeneity of group participants (e.g., including users and nonusers of a particular child care service within the same focus group) potentially heads off these problems by stimulating different points of view and a depth of understanding that comes from listening to participants “defend” their way of thinking (e.g., product or service preferences). As Grønkjær et al. (2011) state, “a group may be too homogeneous; thus influencing the range and variety of the data that emerges” (p. 26). The tension that heterogeneity may create in a group discussion can serve to uncover deeper insights into what is being studied, providing the moderator is able to channel this tension in constructive directions. In addition to a heightened level of diversity, heterogeneous groups may also be a very pragmatic choice for the researcher who is working with limited time and financial resources, or whose target population for the research is confined to a very narrow group (e.g., nurses working at a community hospital).
Ultimately, the answer to the question of whether group participants should be homogeneous or heterogeneous is “it depends.” As a general rule, group participants should have similar experiences with, or knowledge of, the research topic (e.g., using the Web to diagnose a health problem, weekly consumption of fat-free milk), but the need for “sameness” among participants on other parameters can fluctuate depending on the circumstance. Halcomb, Gholizadeh, DiGiacomo, Phillips, and Davidson (2007), for example, report that homogeneity of age is particularly important in non-Western countries where younger people may believe it is disrespectful to offer comments that differ from those stated by their elders. Homogeneous groups are also important when investigating sensitive topics, such as drug use among teenagers, where a more mixed group of participants with people who are perceived as “different” (in terms of demographics and knowledge/experience with drugs) may choke the discussion and lead to a struggle for control among participants (e.g., one or more participants trying to dominate the discussion).
Homogeneity of gender, on the other hand, may or may not be important to the success (usefulness) of a focus group study. For example, an organization conducting employee focus group research to explore employees’ attitudes toward recent shifts in management would need to conduct separate groups with men and women in order to discover how the underlying emotional response to new management differs between male and female employees. In contrast, a focus group study among city residents concerning public transportation might benefit from including both men and women in the same discussion, among whom the varied use and perceptions of the transportation services would serve to stimulate thinking and enrich the research findings. The heightened level of dynamics in groups that are heterogeneous in gender and other aspects may also provoke conversations on taboo subjects (e.g., racism) that might not be forthcoming in other methods such as in-depth interviews.
Grønkjær, M., Curtis, T., de Crespigny, C., & Delmar, C. (2011). Analysing group interaction in focus group research: Impact on content and the role of the moderator. Qualitative Studies, 2(1), 16–30.
Halcomb, E. J., Gholizadeh, L., DiGiacomo, M., Phillips, J., & Davidson, P. M. (2007). Literature review: Considerations in undertaking focus group research with culturally and linguistically diverse groups. Journal of Clinical Nursing, 16(6), 1000–1011. https://doi.org/10.1111/j.1365-2702.2006.01760.x
Sim, J. (1998). Collecting and analysing qualitative data: Issues raised by the focus group. Journal of Advanced Nursing, 28(2), 345–352. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/9725732
Images captured/created from: https://www.thoughtco.com/heterogeneous-definition-and-example-606355
Research Design Review 
Design decisions about focus groups – should be deliberate (unless it’s with a naturally occurring group). However, as with any research endeavor – what drives design decisions – is/are the research question(s) being asked.
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Thank you, Joe, for the comment. Indeed, it is all about the research question(s) — and the type of participants needed to address the objectives — that guide all sorts of design decisions. Reflecting on the type of participants and the objectives is important to the heterogeneity-homogeneity consideration.
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