To estimate the prevalence of injecting drug use, a researcher recruits initial participants through a de-addiction centre and asks each participant to refer other injecting drug users known to them. This sampling method is:

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

Explanation

Snowball sampling relies on existing participants recruiting further members of their own network, making it the standard approach for hidden or hard-to-reach populations such as injecting drug users, commercial sex workers, or homeless persons. Convenience sampling simply takes whoever is easily available without a referral chain. Purposive sampling selects subjects by judgement against set criteria, and quota sampling fills predetermined numbers in subgroups. The referral chain is the defining feature here.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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