Question

If E denotes expectation,the variance of a random variable X is given by

• A. $E\left(X^2\right)-E^2\left(X\right)$
• B. $E\left(X^2\right)+E^2\left(X\right)$
• C. $E\left(X^2\right)$
• D. $E^2\left(X\right)$

Answer 1

The correct option is A $E\left(X^2\right)-E^2\left(X\right)$

Standard result:

$Var\left(X\right)=E\left(X^2\right)-E^2\left(X\right)$