Depending on what the particular needs are for a qualitative study, the samples should be small so that researchers can achieve data saturation, in which no new information is encountered so that redundancy occurs (Polit & Beck, 2008, p. 363). In comparison, quantitative studies are usually advantaged by larger samples that are more representative of a population.
Developing a sample for a research study requires researchers to specifically tailor their sample to the research design. Doing so involves determining whether the study will be quantitative or qualitative, and utilizing one of the many different sampling measures that categorized as either nonprobability or probability sampling. There is a distinct relationship between quantitative studies and probability sampling measures, and qualitative research and non-probability measures (particularly those that involve purposive sampling). However, researchers must ensure that their samples demonstrate a causal relationship -- that is ideally in accordance with their hypotheses -- and that it demonstrates a contrasting of independent and dependent variables....
Additionally, sampling concerns should also show some form of consideration of biases and threats to the integrity of data, which may produce erroneous conclusions.
References
Creswell, J. (2002). Research Design: Qualitative, Quantitative, and Mixed Method Approaches. Thousand Oaks: Sage Publications. Retrieved from http://files.myopera.com/caohockinhtek21/blog/Qualitative,%20Quantitative,%20and%20mixed%20methods.pdf
Lunsford, T.R., Lunsford, B.R. (2005). "Research forum -- the research sample, part I: Sampling." American Academy of Orthotists & Prosthetists. Retrieved from http://www.oandp.org/jpo/library/1995_03_105.asp
No author. (no date). "What is research design." Esf-agentschap.be. Retrieved from Polit, D.F., & Beck, C.T. (2008). Nursing Research: Generating and Assessing Evidence for Nursing Practice, (8th ed.). Philadelphia: Lippincott, Williams, & Wilkins. ISBN 9780781794688
Saldanha, L., Thompson, P. (2002). "Conceptions of sample and their relationship to statistical inferences." Educational Studies in Mathematics. 51 (3) 257-270.
