Thread: how to get the variance of X^2

The expectation of X---E(X) and the variance of X---VAR(X) has been given, but no other more condition, can we solve the variance of X^2---VAR(X^2)? Thank you for your help！

Originally Posted by lyb66

The expectation of X---E(X) and the variance of X---VAR(X) has been given, but no other more condition, can we solve the variance of X^2---VAR(X^2)? Thank you for your help！

Var(X^2) = E(X^4) - (E(X^2))^2. The second term is easy to get, the first term cannot be got without further information.