In a study on hypertension prevalence, the mean SBP is 135 mmHg with a standard deviation of 15 mmHg. The distribution is perfectly normal. What percentage of the population has SBP between 105 mmHg and 165 mmHg?
- A 68.3%
- B 95.4% ✓
- C 99.7%
- D 88.8%
Correct answer: B. 95.4%
Explanation
105 mmHg = mean − 2SD (135−30) and 165 mmHg = mean + 2SD (135+30). The range mean ± 2SD encompasses 95.4% of a normally distributed population. Mean ± 1SD covers 68.3% and mean ± 3SD covers 99.7%. Option D has no standard statistical basis.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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