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Compute the variance of the following frequency distribution. Class mark x: 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5 Frequency f: 3, 7, 22, 60, 85, 32, 8

1. 1.29
2. 2.19
3. 1.32
4. none of these

Correct answer: 1.32

Solution

Computing the mean and the mean of squares for the 217 observations gives a variance of about 1.32.

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