In a large population study, fasting blood sugar values follow a normal distribution with mean 100 mg/dL and SD 10 mg/dL. Approximately what percentage of individuals will have values between 90 and 110 mg/dL?
- A 99.7%
- B 95%
- C 68% ✓
- D 50%
Correct answer: C. 68%
Explanation
In a Gaussian distribution, mean plus or minus one SD covers about 68% of observations, mean plus or minus two SD covers 95%, and mean plus or minus three SD covers 99.7%. Here 90 to 110 mg/dL is exactly one SD on either side of the mean. Option B corresponds to the 80 to 120 mg/dL range, which is the most tempting distractor because 95% intervals are quoted most often.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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