Group A has a mean haemoglobin of 12 g/dL with SD 1.2 g/dL. Group B has a mean serum sodium of 140 mEq/L with SD 7 mEq/L. To decide which group shows greater relative dispersion, the correct measure is:

• A Standard deviation of each group
• B Standard error of the mean of each group
• C Range of each group
• D Coefficient of variation of each group ✓

Explanation

The coefficient of variation, calculated as SD divided by mean multiplied by 100, expresses variability relative to the magnitude of the measurement and is unit-free. It allows comparison of dispersion between variables measured in different units, here g/dL versus mEq/L. Group A has CV 10 percent and Group D has CV 5 percent, so Group A is relatively more variable. Raw SDs cannot be compared across different units.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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