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Classes 0-10 and 10-20 have frequencies 3 and 1. The variance of the grouped data is
A25
B75
C6.25
D18.75
Answer & Solution
Correct answer: D. 18.75
With mid-points 5 and 15 and mean 7.5, 3(2.5 squared) + 1(7.5 squared) = 75, and 75/4 = 18.75.
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