A researcher studying injecting drug use wants to recruit hidden populations not listed in any sampling frame. Initial contacts refer other members of their network, who in turn refer further contacts. This technique is:

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

Explanation

Snowball sampling, also called chain referral sampling, builds the sample through referrals from initial subjects and suits hidden or hard-to-reach groups such as injecting drug users or commercial sex workers. Convenience sampling simply takes whoever is easily available without a referral chain, and quota sampling fills preset quotas from different subgroups. All of these are non-probability methods, so none permits valid statistical generalisation to the population.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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