What characterises a good sample in qualitative research?

VickyRN, MSN, DNP, RN · May 29, 2011

In qualitative research, it is common practice to enroll a relatively small number of “information rich” candidates to contribute to a study. The goal of the sampling method is not to generalize, but rather to see the patterns emerging from a variety of backgrounds. The proposed sample size should be one that is adequate in achieving data saturation (i.e., recurrent patterns, emerging themes). Two sampling methods that are frequently used in qualitative research are purposive sampling and snowball sampling.

Purposive sampling is a type of nonprobability sampling in which the investigator deliberately seeks cases with certain characteristics that best suit the purpose of the study. Cases may be typical, extreme, or negative exceptions. With typical cases, the sample is selected subjectively and nonrandomly to target people who are excellent models of the phenomenon under study and to exclude those who are not. With snowball sampling, the researcher asks participants to refer other people who fit the study requirements and then the researcher follows up with these potential new subjects. As such, snowball sampling is useful for accessing difficult-to-reach populations. A disadvantage to both sampling techniques is the strong possibility of bias and error and a sample that may not be representative of the entire population.

Here are some authoritative sources on the subject you may find helpful:

http://spa.hust.edu.cn/2008/uploadfile/2009-9/20090916221539453.pdf

http://www.quirks.com/articles/a2000/20001202.aspx?searchID=215035&sort=5&pg=1

http://www.ncbi.nlm.nih.gov/pubmed/7899572

http://www.ehow.com/how_6076933_choose-sample-size-qualitative-research.html

http://www.uncp.edu/home/marson/qualitative_research.html

http://scholar.lib.vt.edu/ejournals/JTE/v9n1/hoepfl.html

http://www-distance.syr.edu/qualproposal.html