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The calculation formula of variance I'm going to dictate it, inside [variance formula s ^ 2 = 1 / n [(x1-m) ^ 2 + (x2-m) ^ 2 +... + (xn-m) ^ 2] I don't understand this. I only remember the x1-x pull-out or something
Well, here, M is the mathematical expectation, that is, the mean value, that is, the following x-pull, which means the same thing
Mathematical expectation ex = (x1 + x2 +... + xn) / n
Variance DX = [(x1 Ex) square + (x2 Ex) square +... (xn Ex) square] / n
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