In a study of systolic blood pressure in 100 men, the SD of individual readings is 15 mmHg. The standard error of the mean will be:

• A 1.5 mmHg ✓
• B 15 mmHg
• C 3 mmHg
• D 0.15 mmHg

Explanation

Standard error of the mean equals SD divided by square root of sample size, here 15 divided by square root of 100, giving 1.5 mmHg. The SEM quantifies the precision of the sample mean as an estimate of the population mean and shrinks as sample size grows, whereas the SD describes scatter of individual observations around their mean. Confusing these two is among the commonest errors in interpreting published results.

Reference: Mahajan's Methods in Biostatistics for Medical Students, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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