Q.In a college, the marks obtained by students in Economics have a mean of 50 and a Standard Deviation of 5, while their marks in Accountancy have a mean of 60 and a Standard Deviation of 9. Compare the two subjects using the Coefficient of Variation and state which shows more consistent performance.

Coefficient of Variation lets two series with different average levels be compared for consistency on a common, unit-free scale. …

Step 1 — CV for Economics.

Step 2 — CV for Accountancy.

$CV_{Acc} = \frac{\sigma}{\bar{X}} \times 100 = \frac{9}{60} \times 100 = 15\%$ …

Cross-check by rescaling. If Accountancy's mean is hypothetically brought down to Economics' level of 50 (scaling both mean and SD by the same factor 50/60), its equivalent SD becomes $9 \times \frac{50}{60} = 7.5$, which is still greater than Economics' ac …

Comparing the two subjects' Standard Deviations DIRECTLY (9 > 5) and wrongly concluding Accountancy is more variable without first converting to a common, mean-adjusted basis — this is exactly the comparison error the Co …