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For a data set of 15 values of X, the given totals are Σx² = 2830 and Σx = 170. Later, one entry recorded as 20 was discovered to be incorrect and was changed to the correct value 30. The variance after this correction is

1. 78.00
2. 188.66
3. 177.33
4. 8.33

Correct answer: 78.00

Solution

Corrected sums: Sx = 170 - 20 + 30 = 180, Sx2 = 2830 - 400 + 900 = 3330. Variance = 3330/15 - (180/15)^2 = 222 - 144 = 78.

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