A researcher wants to estimate the prevalence of injecting drug use in a city. Because members of this hidden population are difficult to identify through conventional sampling frames, initial participants are asked to refer other injecting drug users they know. This technique is:

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

Explanation

Snowball sampling is a non-probability method in which initial subjects recruit further subjects from among their contacts, and it is the standard approach for hard-to-reach or hidden populations such as injecting drug users, commercial sex workers and homeless persons. Purposive sampling relies on deliberate investigator selection by judgement, quota sampling fills preset quotas in subgroups, and convenience sampling simply takes whoever is easily available without referral chains.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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