Who to Invite: A Note about Qualitative Sampling
4/25/22 / Matt Bruce
Among the many strengths of qualitative research, sampling is one of the most important yet least appreciated. Sampling is the process of deciding who to invite to participate in your study, and it is key to both quantitative research (e.g., surveys) and qualitative research (e.g., focus groups and in-depth interviews). While representativeness via randomness is the staple of most survey sampling, qualitative sampling takes a different path – one that leverages what is already known about the population to reveal deeper insights.
There are several different qualitative sampling techniques, but let’s focus on just two: maximum variation and homogeneity. Luckily, their names describe how they work. The goal of maximum variation sampling is to define a sample of participants who are extremely different from each other. For example, you may delineate a sample of people who live in different areas, are of different ages and genders, hold different education levels, and have had different life experiences. Many clients appreciate maximum variation sampling, especially in focus group research. The key advantage of this sampling approach is that any commonalities that emerge from such great variation of people are likely to be important and insightful. But there are two important caveats to note. First, maximum variation does not necessarily mean that the results will be more representative of a broader population. Indeed, a good maximum variation sample may be more diverse than a meeting of the United Nations! Second, this approach is likely to require engaging far more research participants for common themes to emerge, if they do at all. Finding and interviewing more participants requires more time and money, so consider the trade-offs before taking this approach.
Conversely, the goal of homogeneity sampling is to define a sample of participants who hold many similarities. For example, you may decide to sample only young Hispanic women who are studying psychology. The key advantage of homogeneity sampling is that you quickly reduce the variability within your sample. This enables the researcher to proceed with laser focus on the research topic, because the contextual factors have largely been accounted for in the sampling method itself. An added benefit of homogeneity sampling is that a smaller sample is often sufficient to uncover the salient issues. However, good researchers should always be on the lookout for additional context variables that cannot be accounted for through sampling alone.
These two sampling techniques are the endpoints of an irregular continuum of qualitative sampling approaches, with many other approaches in between. Limiting your research to only one sampling approach is not needed; good qualitative studies often use a combination of sampling techniques to make the most of time and talent. If the sampling plan is deliberate and thoughtful, you will be fast on your way to better insights.