The answer to this question, of course, depends on your specific research question. However, it is useful to review what has been done in the previous literature. An article by Vasileiou et al. (2018) A systematic literature review was conducted of all studies published using single-interview-per-participant designs in three health-related journals: the British Medical Journal (BMJ), the British Journal of Health Psychology (BJHP) and the Sociology of Health & Illness (SHI). Studies published in these three journals between January 2003 and September 2017 were assessed.
Overall, the average number of interviews was 31. British Journal of Medicine15 for BJHPand 30.5 for SHIMore information on the distribution of respondents per study is shown in the following graph.
Overall, 72.0% of the articles do not justify the chosen sample size. By journal, “Just over 50% of articles in BMJ and BJHP and 82% in SHI provided no justification for sample size.”
What rationales did the authors use to justify their sample size? Saturation was the most common, followed by pragmatic considerations.
You can find more details and examples of these justifications by reading the full article. here.
