Definition
Non-probability sampling selects participants through deliberate choice or accessibility rather than random chance, focusing on relevance or practicality.

Introduction
Not every study aims to generalize statistically. Exploratory, qualitative, and pilot research often seek understanding rather than representativeness. In such cases, purposive selection allows deeper insight within constrained contexts.

Explanation

Convenience Sampling recruits whoever is readily available—students in a class, customers in a mall.

Purposive Sampling involves expert judgment: selecting cases rich in information.

Quota Sampling ensures certain categories reach set proportions without randomization.

Snowball Sampling spreads through referrals, ideal for hidden or hard-to-reach groups such as migrants or patients with rare diseases.

While faster and cheaper, non-probability methods risk bias; their strength lies in flexibility and depth. They help generate hypotheses later tested through probability designs.

Key Takeaways
These methods suit early-stage or specialized inquiries where randomness is less crucial than contextual richness.

Real-World Case
Anthropologist Bronislaw Malinowski’s seminal fieldwork among the Trobriand Islanders used purposive immersion—he deliberately studied a small, information-rich community, pioneering modern ethnography.
Reference: London School of Economics Archives