Which sampling method BEST describes deliberate selection of subjects based on predefined criteria?

• A. Convenience sampling
• B. Purposive sampling
• C. Quota sampling
• D. Snowball sampling

Answer: (B)

Purposive sampling means you deliberately choose participants who meet specific criteria that are essential to the study. You define inclusion characteristics in advance and recruit only those individuals who fit them, so the data come from the exact types of cases you need to answer your question. This targeted, criteria-driven approach is what makes it the best description of deliberate selection based on predefined criteria.

For example, in a study evaluating a therapy for a particular knee condition, you would select adults within a defined age range who have that diagnosis, ensuring every participant directly informs the research question.

Convenience sampling picks whoever is easiest to recruit, not based on predefined criteria. Quota sampling aims to fill predetermined subgroups, but the selection within those groups isn’t driven by meeting the study’s specific criteria for each case. Snowball sampling relies on participants referring others, expanding the sample through networks rather than criteria-based recruitment.