Definition

Patton (2001) describes these at samples within samples and suggests that purposeful samples can be stratified or nested by selecting particular units or cases that vary according to a key dimension. 

For example, one may purposefully sample primary care practices and stratify this purposeful sample by practice size (small, medium and large) and practice setting (urban, suburban and rural).

Stratified purposeful sampling is different from stratified random sampling in that the sample sizes are likely to be too small for generalization.

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Why use this method?

A stratified purposeful sampling approach can lend credibility to a research study.

When enough information is known to identify characteristics that may influence how the phenonmenon is manifest, then it may make sense to use a stratified purposeful sampling approach.

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