In a sample of 100 adults, mean haemoglobin is 12 g/dL with a standard deviation of 2 g/dL. What is the standard error of the mean?

• A 0.02 g/dL
• B 2 g/dL
• C 0.2 g/dL ✓
• D 0.5 g/dL

Explanation

Standard error of the mean equals standard deviation divided by the square root of sample size, here 2 divided by the square root of 100, giving 0.2 g/dL. The SEM quantifies the precision of the sample mean as an estimate of the population mean and shrinks as sample size grows. Option B confuses SEM with the standard deviation itself, which describes individual variability around the mean rather than reliability of the mean estimate.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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