Sample size for qualitative research

Abstract

Purpose Qualitative researchers have been criticised for not justifying sample size decisions in their research. This short paper addresses the issue of which sample sizes are appropriate and valid within different approaches to qualitative research. Design/methodology/approach The sparse literature on sample sizes in qualitative research is reviewed and discussed. This examination is informed by the personal experience of the author in terms of assessing, as an editor, reviewer comments as they relate to sample size in qualitative research. Also, the discussion is informed by the author’s own experience of undertaking commercial and academic qualitative research over the last 31 years. Findings In qualitative research, the determination of sample size is contextual and partially dependent upon the scientific paradigm under which investigation is taking place. For example, qualitative research which is oriented towards positivism, will require larger samples than in-depth qualitative research does, so that a representative picture of the whole population under review can be gained. Nonetheless, the paper also concludes that sample sizes involving one single case can be highly informative and meaningful as demonstrated in examples from management and medical research. Unique examples of research using a single sample or case but involving new areas or findings that are potentially highly relevant, can be worthy of publication. Theoretical saturation can also be useful as a guide in designing qualitative research, with practical research illustrating that samples of 12 may be cases where data saturation occurs among a relatively homogeneous population. Practical implications Sample sizes as low as one can be justified. Researchers and reviewers may find the discussion in this paper to be a useful guide to determining and critiquing sample size in qualitative research. Originality/value Sample size in qualitative research is always mentioned by reviewers of qualitative papers but discussion tends to be simplistic and relatively uninformed. The current paper draws attention to how sample sizes, at both ends of the size continuum, can be justified by researchers. This will also aid reviewers in their making of comments about the appropriateness of sample sizes in qualitative research.

An inductive qualitative approach to explore Nurse Practitioners views on leadership and research: An international perspective

“…Whilst data saturation was a useful determinant of sample size at a conceptual level, a premeditated pragmatic model was also used to guide sampling (Boddy, ; Malterud, Siersma, & Guassora, ). The pragmatic model determined that six to ten participants would be required to synthesise and build on knowledge learned from phase one of the research (Malterud et al, ).…”

HIV/AIDS‐related beliefs among Israeli Arab‐Palestinian women

“…Since the data collection process and analysis were parallel, the sample was completed at the same time that the data set was finalised, and the replication of the data was secured. Therefore, sufficient data on all aspects of the studied phenomenon were collected (Boddy, ; Morse, Barrett, Mayan, Olson, & Spiers, ).…”

Perception of physical health by patients with severe mental illness and their family caregivers: A qualitative study

“…Participants were selected using a purposive sampling method. According to the qualitative research method, the number of samples is determined during interviews by extracting information until it is repeated and no new information emerges (a saturation point) . In the present study, the number of samples was determined when the data reached the saturation point.…”