E(X-EX)^2怎么等于EX^2-(EX)^2
问题描述:
E(X-EX)^2怎么等于EX^2-(EX)^2
答
E(X-EX)^2=E(X^2-2XEX+(EX)^2)=E(X^2)-E(2XEX)+E(EX)^2)=E(X^2)-2(EX)^2+(EX)^2)=EX^2-(EX)^2
E(X-EX)^2怎么等于EX^2-(EX)^2
E(X-EX)^2=E(X^2-2XEX+(EX)^2)=E(X^2)-E(2XEX)+E(EX)^2)=E(X^2)-2(EX)^2+(EX)^2)=EX^2-(EX)^2