In a screening program, 15 out of 150 individuals tested positive for a disease. The 95% confidence interval for the true population proportion is approximately:
- A 1.0% to 19.0%
- B 5.2% to 14.8% ✓
- C 7.0% to 13.0%
- D 10.0% to 20.0%
Correct answer: B. 5.2% to 14.8%
Explanation
Sample proportion p = 15/150 = 0.10. Standard error = sqrt(0.10 x 0.90 / 150) = 0.0245. The 95% CI is 0.10 +/- 1.96 x 0.0245, giving 0.052 to 0.148 (5.2% to 14.8%). Option A is too wide, option C is too narrow, and option D is not centered correctly.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
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