How should the number of subjects for participation in a qualitative study be determined?

The number of subjects for participation in a qualitative study should be determined by the principle of data saturation, which occurs when no new themes or insights are emerging from the data. Researchers often start with a smaller sample size, typically between 5 to 30 participants, and then continue to recruit until they reach saturation. Additionally, the complexity of the research question, the diversity of the population, and the specific methodology used can also influence the final sample size. It's essential to balance depth of insight with practical considerations such as time and resources.