A health survey uses stratified random sampling to ensure representation from rural and urban areas. The urban stratum has 10,000 people and the rural stratum has 40,000 people. Using proportional allocation with a total sample of 1,000, how many should be sampled from the urban stratum?
- A 200 ✓
- B 500
- C 400
- D 800
Correct answer: A. 200
Explanation
In proportional stratified sampling, the sample size from each stratum is proportional to the stratum's share of the total population. Total population = 50,000. Urban proportion = 10,000/50,000 = 0.20. Urban sample = 0.20 × 1,000 = 200. Rural sample = 0.80 × 1,000 = 800. This method ensures that larger strata contribute proportionally more to the sample, maintaining representativeness.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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