Purposive Sampling
Methodology & design
Non-probability sampling that deliberately selects information-rich cases against explicit criteria — the default sampling logic of qualitative research.
Purposive sampling selects participants deliberately because they possess characteristics relevant to the research question. It is a non-probability technique, and in qualitative research it is the appropriate default: the goal is information-rich cases, not a statistically representative cross-section.
Recognised variants serve different purposes. Maximum variation sampling deliberately spans diverse cases to identify patterns that hold across them; homogeneous sampling narrows to one subgroup for depth; critical case sampling selects cases that make a point decisively; and extreme or deviant case sampling targets unusual instances that illuminate the norm.
The requirement is explicit, defensible selection criteria stated in advance — the characteristics a participant had to have, and why those characteristics matter to the question. Because it does not support statistical generalisation, findings transfer through the reader's judgement, which is why thick description of the sample and setting matters.
Where it's used
- Selecting interview participants who have lived the phenomenon
- Choosing critical or extreme cases for case-study research
Related concepts
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