A large study finds that the mean serum cholesterol in a population is 200 mg/dL with a standard deviation of 40 mg/dL. Assuming a normal distribution, approximately what percentage of the population has cholesterol between 160 and 240 mg/dL?
- A 99.7%
- B 95%
- C 68% ✓
- D 50%
Correct answer: C. 68%
Explanation
The range 160 to 240 mg/dL represents mean ± 1 standard deviation (200 ± 40). In a normal distribution, approximately 68% of values lie within one standard deviation of the mean. The 95% range would be mean ± 2 SD (120 to 280), and 99.7% would be mean ± 3 SD (80 to 320). This is the empirical rule fundamental to biostatistics.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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