Qualitative Research Sampling
By Sharon Warkentin Short
To me, one of the most intriguing aspects of qualitative research is the selection of the sample with whom to conduct the study. In contrast to the probability or random sampling that is standard for quantitative investigations, qualitative researchers generally rely on “nonprobabilistic” (Merriam, 1998) or nonrandom sampling to determine their research participants. That is to say, rather than selecting individuals or groups in such a way that each member of the population under study has an equal chance of being chosen, qualitative inquirers deliberately seek out respondents who have the most to contribute: “the goal is to select cases that are likely to be ‘information-rich’ with respect to the purposes of the study” (Gall et al., 2003, p. 165). This selection approach has sometimes been labeled “purposive” or “purposeful sampling” (Merriam, 1998).
An instructive way to think about purposeful sampling is to view such participants as panels of experts in a specific area (Maxwell, 2005), comparable to medical specialists who are consulted regarding a difficult case. In that situation, the goal is not to get an average opinion from an entire population of doctors, but rather to hear what these particularly qualified people have to say (Merriam, 1998). At least fifteen different varieties of purposeful samples have been identified (Gall et al., 2003).
For my research I decided that an intensity sample was the best choice. Described as “cases that manifest the phenomenon of interest intensely but not extremely” (Gall et al., 2003, p. 178), such informants can be expected to provide ample useful data without seeming so rare or exceptional that subsequent readers of the research might feel the study has nothing relevant to say to them.
When I was first exposed to the whole area of nonrandom research sampling, I was very skeptical, because it sounded so contradictory to the tenets of objective, scientific research. However, it was the analogy of the panel of medical experts that convinced me. I realized that, for my study, I was not trying to discover what “average” children, or children in general, thought about Bible stories; I wanted to watch closely how one particular group of children in one Sunday school responded to the stories. The sample that I eventually studied constituted an intensity sample in that their church was field-testing a new children’s curriculum organized around the metanarrative of the Bible. This meant that the teaching materials were explicitly focused on Bible stories, and the volunteers and staff were committed to using the materials as effectively as possible. In this program they were more involved with the Bible stories than a typical Sunday school class might have been, but their involvement was not out of reach for most churches.
Gall, M. D., Gall, J. P., & Borg, W. R. (2003). Educational research: An introduction (7th ed.). Boston: Allyn and Bacon.
Maxwell, J. A. (2005). Qualitative research design: An interactive approach (2nd ed.). Vol. 41. Applied Social Research Methods Series. Thousand Oaks, CA: Sage.
Merriam, S. B. (1998). Qualitative research and case study applications in education (Rev. ed.). San Francisco: Jossey-Bass.