Question

A distribution x is known to have a mean value of 5 and a standard deviation of 5. what is its mean square value (i.e., the expected value of x2)?

Answer 1

$\mathbb V(X)=\mathbb E(X^2)-\mathbb E(X)^2$
$\implies 5^2=\mathbb E(X^2)-5^2$
$\implies\mathbb E(X^2)=50$