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If X is a discrete random variable with probability measure function
2
f(x)= 1/11 , x=1,2,...,11. Then σ is ?
x
2 (N^2)-1 (11^2) -1
我的書本是這樣寫的: σ = --------- = ----------- = 10
x 12 12
我想知道說這個方法是怎麼出來的。因為我看到題目只會直接
用 Var(X)=E(X^2)-(E(X))^2
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