Bad participant selection kills studies before they start. Nielsen Norman Group's latest breaks down how to define selection criteria that go beyond age and job title, targeting the behavioral and attitudinal traits that actually determine whether a participant can answer your research question.
The article opens with a concrete failure mode: a fitness tool study where participants show up with zero interest in fitness, data scatters, and the team walks away with nothing actionable. That scenario is the architecture of the whole piece. NNG uses it to build out three distinct criteria types: inclusion, exclusion, and diversity, each serving a different function in protecting study validity and preventing costly misrecruits.
The full article is worth reading for the operational specifics, namely how to translate a research question into screener logic, where diversity criteria differ from simple demographic quotas, and why exclusion criteria are as strategically important as inclusion ones. If you recruit participants for qualitative or usability work, this is a checklist you will use.
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