Question

方差变形公式的推倒过程

Answer 1

方差D=d^2（d为均方差）

D(x)=E{[x-E(x)}^2}=E{x^2-2xE(x)+[E(x)]^2}=E(x^2)-2E(x)E(x)+[E(x)]^2

=E(x^2)-[E(x)]^2