Sampling for Qualitative Research
Sampling, as it relates to research, refers to the selection of individuals, units, and/or settings to be studied. Whereas quantitative studies strive for random sampling, qualitative studies often use purposeful or criterion-based sampling, that is, a sample that has the characteristics relevant to the research question(s). For example, if you are interested in studying adult survivors of childhood sexual abuse, interviewing a random sample of 10 people may yield only one adult survivor, thus, you will essentially have a sample size of one and need to continue to randomly sample people until you have interviewed an appropriate number of who have survived childhood sexual abuse. This is not a wise use of your time.
The difference in sampling strategies between quantitative and qualitative studies is due to the different goals of each research approach. Recall that typical quantitative research seeks to infer from a sample to a population (for example, a relationship or a treatment effect). In general, you want to include a variety of types of people in a quantitative study so that it generalizes beyond those in your study. Thus, the goal of quantitative approaches can be stated as, ”empirical generalization to many.”
Qualitative research, on the other hand, typically starts with a specific group, type of individual, event, or process. As in the qualitative study of adult survivors of childhood sexual abuse example above, you would choose your sample very purposefully and include in your study only those with this particular experience. The goal of qualitative research can be stated as “in-depth understanding.”