A sample of 100 schoolchildren has mean weight 28 kg with standard deviation 5 kg. The standard error of the mean is:
- A 0.05 kg
- B 0.5 kg ✓
- C 5 kg
- D 25 kg
Correct answer: B. 0.5 kg
Explanation
Standard error of the mean equals SD divided by the square root of n, that is 5 divided by the square root of 100, giving 0.5 kg. It quantifies the precision of the sample mean as an estimate of the population mean. Confusing SE with SD gives 5 kg, the commonest error, while squaring instead of taking the root produces 25 kg.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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