A researcher studying injecting drug users recruits initial participants through a needle exchange clinic and asks each participant to refer other members of the same hidden network. This sampling method is known as:

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

Explanation

Snowball sampling builds the sample through referrals from existing participants and is the standard approach for hard-to-reach populations whose sampling frame cannot be enumerated, such as drug users, sex workers or undocumented migrants. Purposive sampling selects participants deliberately for specific characteristics without referral chains, while convenience sampling simply takes whoever is accessible without using participant networks to extend recruitment.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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