Question

Discuss the issue of sample size in qualitative research. How might a qualitative researcher determine an appropriate sample size? What influence does sample size have on transferability?

Answer 1

Qualitative research require a smaller sample size than quantitative research. As in quantitative we are trying to achieve a satisfactory statistical result from a large sample size, qualitative requires a more diverse sample which satisfy every criterion of the aim of the study/research we are performing. Hence, the right study group selected from the population matters a lot.
Then, the size of the sample gets influenced by the "Principle of Saturation". As we want to decrease the chances of failure of our discovery, we want the most appropriate sample size that defines our interest and answers our research question at hand. A researcher can use this principle to determine an apt size. He/she can start with a small sample size and keep on adding more participants in the sample until adding does not yield in any new information or discovery.
Some researchers have suggested the following sizes for different fields of qualitative research like for ethnography study we may select 30 – 50 participants. For grounded theory, 30 – 50 interviews. For phenomenological studies, 5 –25. These suggestions can help to get an idea of sample size but the rule of saturation should be at the foremost while on the hunt of the size.

Sample size can have a heavy influence on transferability as our study group should be following all or most of the criterion set by our research aim and our interest in the target population. It should also be partitioned, if required, according to the sample design to attain highest credibility. If we can obtain a robust conclusion based on the evidence provided by the sample that was large enough to accommodate diversity but not huge, as the data gets repetitive after a while. Then the other reaswarchers can apply our conclusions across different times and situations.
Therefore selecting a sample size is the most important step in the qualitative research.