A sampling strategy for qualitative research.

This paper discusses sampling in qualitative research, describing the principles and how different researchers have described their sampling techniques. The example of a research project in which the authors were involved ( 1 ) is used to show how a range of quantitative and qualitative sampling techniques can be combined, highlighting some of the problems. In particular, where theoretical sampling was required, we found that a systematic way of identifying theoretically useful sampling units was needed, and so a method of selection which we have called matrix sampling was devised, whereby informed and coherent choices could be made.