Which of the Following Formulas Will Compute the Variance of a Discrete

Multiple Choice

Which of the following formulas will compute the variance of a discrete random variable X?

A) $\sum_{j=1}^{n}\left(x_{j}-E[X]^{2}\right)$

B) $\sum_{j=1}^{\infty} \mathrm{E}[X]^{2} f\left(x_{j}\right)$

C) $\sum_{j=1}^{\infty}\left(x_{j}-E[X]\right) ^{2} f\left(x_{j}\right)$

D) $\sum_{j=1}^{\infty}\left(x_{j}\right) 2 f\left(x_{j}\right)$