A study reports a mean serum creatinine of 1.2 mg/dL with a standard error of the mean of 0.1 mg/dL from a sample of 100 patients. If the study were repeated with 400 patients and the same standard deviation, the standard error of the mean would be:

• A 0.4 mg/dL
• B 0.2 mg/dL
• C 0.05 mg/dL ✓
• D 0.025 mg/dL

Explanation

Standard error of the mean equals the standard deviation divided by the square root of sample size. Quadrupling the sample size from 100 to 400 increases the denominator from 10 to 20, halving the SEM from 0.1 to 0.05 mg/dL. SEM decreases as sample size increases, reflecting greater precision of the sample mean estimate.

Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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