Adaptive Purposive Sampling — Iterative Purposeful Case Selection

Adaptive purposive sampling is a qualitative strategy in which the researcher begins with explicitly stated, theory-driven selection criteria and then deliberately revises those criteria as data collection proceeds and new understanding emerges. Unlike fixed purposive sampling — where criteria are locked in before fieldwork — the adaptive variant treats the sampling frame as a working hypothesis that is refined in response to early findings, enabling the study to follow the evidence into unexpected but analytically important directions.