In a newborn cohort, birth weight has a mean of 3.0 kg with a standard deviation of 0.45 kg, while crown-heel length has a mean of 50 cm with a standard deviation of 2.5 cm. To decide which measurement shows greater relative variability within this population, the appropriate statistic is:
- A Coefficient of variation, which is higher for birth weight ✓
- B Standard deviation, since it is larger for length
- C Coefficient of variation, which is higher for crown-heel length
- D Standard error of the mean
Correct answer: A. Coefficient of variation, which is higher for birth weight
Explanation
Because weight and length carry different units, their standard deviations cannot be compared directly. The coefficient of variation expresses relative spread as (SD divided by mean) multiplied by 100. For birth weight this is (0.45/3.0) x 100 = 15 percent, while for length it is (2.5/50) x 100 = 5 percent, so birth weight is relatively more variable. The standard error describes precision of the mean, not dispersion of individual values.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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