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We know that the average of the sum of squares of a group of data is 228, and the average is 15. We can find the variance of this group of data
Suppose: there are n numbers in this group of data, denoted as x1, X2, X3 From the title, we know that ∑ (XI) & sup2; = 228n, ∑ (XI) = 15N, and the variance ∑ & sup2; = ∑ (xi-15) & sup2 / / N = [∑ (XI) & sup2; - 30 ∑ (XI) + 15 & sup2; ∑ 1] / N = [228n-30 * 15N + 15 & sup2; * n] / N = 3 (above, I in ∑ satisfies I = 1,2,3
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