Qualitative research is not concerned with generalising, validity or reliability. Instead, trustworthiness of the research is crucial. Qualitative researchers are after rich, thick account of the voices of participants—the data must be rich in description of the people and places involved (Schurink 1998: 253).
Sampling, therefore, is not about representativeness of the population but purposive, and data saturation—"there is no need to continue interviewing people once the researcher finds that further interviews are not adding to the findings or repeating what was already found in the previous interviews"—a qualitative notion. Guest, Bunce & Johnson (2006) remark that although the notion of saturation is conceptually helpful it does not indicate sample size. They found that data saturation occurred within the first twelve interviews, although basic elements for meta-themes were already present as early as six interviews.
Guest, G., Bunce, A. & Johnson, L. 2006. An Experiment with Data Saturation and Variability. Field Methods, 18( 1), 59-82.
Schurink, E.M. 1998. Designing qualitative research (pp 252-264). In De Vos, A.S. (Ed). Research at grass roots — a primer for the caring professions. Pretoria: van Schaik.