In cluster sampling used for national health surveys, the primary advantage is:
- A Cost-efficiency when a complete sampling frame is unavailable but geographic clustering exists ✓
- B Elimination of sampling error compared to systematic sampling
- C It always gives a lower standard error than simple random sampling
- D Every individual has a known, equal probability of selection from the outset
Correct answer: A. Cost-efficiency when a complete sampling frame is unavailable but geographic clustering exists
Explanation
Cluster sampling is practical and cost-effective when a complete national sampling frame (list of all individuals) is unavailable; geographic clusters (villages, blocks) are sampled first, then all or a random sample of individuals within selected clusters. However, cluster sampling typically has a higher design effect (DEFF) and standard error than simple random sampling for the same sample size due to intra-cluster correlation.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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