Sample Size in Qualitative Research

Gain an understanding of the concept of sample size in qualitative research. In qualitative selecting the most suitable sample size has been an area of conceptual debate and uncertainty (Vasileiou et al., 2018). A common consensus is that sample size in qualitative research is usually small, because of the in-depth nature of the data collected. The focus of this webpage is to discuss what researchers in published literature have recommended on what suitable sample size is in qualitative research.

Does sample size matter in qualitative research? Yes. Let me elaborate. In quantitative research, determining a sample size is usually straightforward because performing a G*Power analysis can result in calculating the most suitable sample size. Contrastingly, in qualitative research, sample size is often subjective because it must be large enough to ensure that almost all the information that could be necessary to gain new insights into a phenomenon under study is collected. At the same time, the sample size should be small enough for in-depth analysis to be conducted. Hence, if you are in a dilemma on how to justify sample size in qualitative research, you must ensure it is large enough to collect adequate data to address the research questions but small enough for in-depth analysis to be performed. The need for qualitative data analysis to be in-depth is why the sample size is small in qualitative research.

This brings us to the question, what should the sample size be for qualitative research? Although there lacks a consensus on the most suitable sample size, different researchers have provided their recommendations. For instance, Hennink and Kaiser (2022) recommended that in a study conducted using interviews, a sample size of 9 to 17 participants would be adequate. The researchers also recommended that if the data collection approach in focus groups, 4 to 8 participants would be appropriate (Hennink & Kaiser, 2022).

In another study, Bekele and Ago (2022) recommended that in a study conducted using narrative research, a sample size of 1 to 2 participants would be enough, while if a grounded theory approach is used, the sample size can be 30 to 50 participants. Comparably, Sim et al. (2018) recommended that for studies conducted using grounded theory, a sample size of 5 to 35 participants should be used, while if a case study design is applied, 4 to 30 participants would be adequate.

Factors that Influence Sample Size in Qualitative Research

Rule of Thumb: The rule of thumb is that in qualitative research, the sample size is usually small.

Data Saturation: Saturation in qualitative research is achieved when new data appears to no longer result in new themes. Rather, from a grounded theory perspective, saturation is the point in data collection where all essential issues or insights have been exhausted from data, signifying that the conceptual categories that make up the theory are saturated, an indicator that the emerging theory is detailed, comprehensive, and adequately grounded in data.

In qualitative research, the determination of sample size is contextual and partly dependent on the design or data collection approach being applied. In the methodology section of your research paper, capstone project, thesis, dissertation, or study, you are required to explain your sample size. If you are experiencing challenges with your qualitative methodology section writing, we can help. We offer qualitative research writing help, which is inclusive of rationalizing the most suitable sample size for your qualitative research.

References

Bekele, W. B., & Ago, F. Y. (2022). Sample size for interview in qualitative research in social sciences: A guide to novice researchers. Research in Educational Policy and Management, 4(1), 42-50.

Sim, J., Saunders, B., Waterfield, J., & Kingstone, T. (2018). Can sample size in qualitative research be determined a priori? International Journal of Social Research Methodology, 21(5), 619-634.

Hennink, M., & Kaiser, B. N. (2022). Sample sizes for saturation in qualitative research: A systematic review of empirical tests. Social Science & Medicine, 292, Article 114523.

Vasileiou, K., Barnett, J., Thorpe, S., & Young, T. (2018). Characterizing and justifying sample size sufficiency in interview-based studies: systematic analysis of qualitative health research over a 15-year period. Biomedical Center medical research methodology, 18, 1-18.