A public health team wants to estimate HIV prevalence among intravenous drug users, a group with no accessible sampling frame who are difficult to identify through routine methods. Initial contacts recruit other users from their own network. This sampling method is:

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

Explanation

In snowball sampling, initial subjects refer further subjects from their social network, so the sample grows like a rolling snowball. It is a non-probability method suited to hidden or hard-to-reach populations such as intravenous drug users, commercial sex workers and men who have sex with men. Quota and purposive sampling rely on researcher selection rather than participant referral, and multistage sampling is a probability method requiring a defined frame at each stage.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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