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In a class, every student scored poorly in Mathematics. The teacher awarded 10 grace marks to each student. Which statistical measure remains unchanged after adding these grace marks to all the scores?
- mean
- median
- mode
- variance
Correct answer: variance
Solution
Adding 10 to every score increases the mean, median and mode each by 10. Variance measures spread about the mean; since every value and the mean shift by the same amount, the deviations are unchanged, so the variance stays the same.
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