Sampling in Qualitative Research, Methods of

Sampling in this type of research is usually purposive (i.e., individuals or groups are selected that will provide the information needed to address the research questions). The goal is always to select information-rich cases when possible. Here, we list and briefly define the major types of sampling used in qualitative research, as identified by Anthony Onwuegbuzie and Nancy Leech (2007). First, in maximum variation sampling, the researcher purposively selects a wide range of cases. Second, in homogeneous sample selection, the researcher selects a small and homogeneous case or set of cases for intensive study. Third, in extreme case sampling, the researcher selects cases that represent the extremes on some dimension. Fourth, in typical-case sampling, the researcher selects typical or average cases. Fifth, in critical-case sampling, the researcher selects cases that are known to be important. Sixth, in negative-case sampling, the researcher purposively selects cases that disconfirm the tentative generalizations being formed, so that the researcher can ensure that he or she is not just selectively finding cases to support his or her personal theory. Seventh, in opportunistic sampling, the researcher selects potentially useful cases as the opportunity arises during fieldwork. Eighth, in mixed purposeful sampling, the researcher mixes and matches the sampling strategies just listed into more complex sampling designs tailored to the needs of the particular research study. Ninth, in theory-based sampling, the researcher selects settings, individuals, and/or groups because their inclusion helps the researcher to develop a theory. Tenth, in confirming/disconfirming sampling, after data collection has commenced, the researcher purposively selects additional cases to verify or confirm the initial findings. Eleventh, in snowball sampling (also called network sampling or chain sampling), the participants already selected for the study are asked to recruit individuals with the same characteristic(s) of interest to join the study. Twelfth, in intensity sampling, the researcher selects settings, individuals, and/or groups because their experiences relative to the phenomena of interest are viewed as intense but not extreme. Thirteenth, in politically important case sampling, the researcher selects settings, individuals, and/or groups to be included or excluded based on their political connections to the phenomenon of interest. Fourteenth, in convenience sampling, the researcher selects settings, individuals, and/or groups that are conveniently available and willing to participate in the research. Fifteenth, in criterion sampling, the researcher selects settings, individuals, and/or groups because they represent one or more criteria. Sixteenth, in quota sampling, the researcher identifies desired characteristics and quotas of sample members to be included in the study. Seventeenth, in random purposeful sampling, the researcher selects random cases from the sampling frame and randomly chooses a desired number of individuals to participate in the study. Eighteenth, in stratified purposeful sampling, the sampling frame is divided into strata to obtain relatively homogeneous subgroups, and a purposeful sample is selected from each stratum. Nineteenth, in multistage purposeful sampling, the researcher selects settings, individuals, and/or groups representing a sample in two or more stages, with all stages reflecting purposive sampling of participants. Finally, in multistage purposeful random sampling, the researcher selects settings, individuals, and/or groups representing a sample in two or more stages, wherein the first stage involves random selection and the following stages involve purposive selection of participants. For more information, see Onwuegbuzie and Leech (2007).

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