In the WHO 30-cluster survey design recommended for estimating immunisation coverage in India, villages are selected with probability proportional to their population size. Which sampling principle does this reflect?
- A Probability proportionate to size sampling ✓
- B Equal probability selection method
- C Non-probability convenience sampling
- D Systematic random sampling
Correct answer: A. Probability proportionate to size sampling
Explanation
Probability proportionate to size sampling assigns larger clusters a correspondingly higher chance of selection, so every individual ultimately has roughly equal probability of inclusion despite unequal cluster sizes. This is the basis of the WHO expanded programme on immunisation 30-cluster technique widely used in Indian coverage surveys. Simple random sampling, by contrast, gives every unit an identical selection probability.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.