What is Typical Case Sampling>
Typical Case Sampling allows you to develop a profile about what is usual or average for a particular phenomenon. For example, let’s say you were studying violence in schools. The first step would be to list all of the criteria that define violence for a “typical” school. Then you would choose schools that meet that criteria. You would want to select schools that are “average” (meeting your selected criteria) instead of schools with very high or very low violence rates.
“Typical” in non probability sampling doesn’t have the same meaning as a typical result from probability sampling methods like simple random sampling. In probability sampling, a typical result would be one that reflected the average result found in the whole population. For example, if your population weighed around 200 pounds, then your typical member would also weight about 200 pounds. In non probability sampling, a typical case means that you can use your findings to cross-compare between samples — or cross check your results with similar studies (as opposed to comparing your results with what would be expected in a population).
Like most non-probability sampling methods, typical case sampling is less than ideal and is usually used when there are severe limitations on time or resources (Henry, 1990). This type of sampling is typically subjected to close scrutiny, so you should take steps to avoid pitfalls like selection bias or minimize their impact. For example, a simple way to minimize selection bias is to avoid including any extreme cases in your sample.
Another limitation with this type of sampling is that you may not be able to deduce what a “typical” case may be. One solution is to ask as many experts in the field as possible what they would consider to be typical cases. Another option is to use another sampling technique — like maximum variation sampling — to identify typical cases prior to choosing cases for your study (Baran, 2016). You could also use demographic data to identify your cases. Wolcott (1994) used a National Education Survey, which reported the typical school principal was “a male, married, between the ages of 35 and 49, has had 10-19 years total experience in schools, and was an elementary classroom teacher” (Wolcott, 1994, p.117); He then looked for a person fitting that description.
Baran, M. (2016). Mixed Methods Research for Improved Scientific Study. IGI Global.
Henry, G. (1990). Practical Sampling. SAGE publications.
Wolcott, H. (1994). Transforming Qualitative Data. Description, Analysis, and Interpretation. SAGE publications.