Mark the correct alternative in the following question:

Let X be a discrete random variable. Then the variance of X is

(a) E(X²) (b) E(X²) + (E(X))² (c) E(X²) $-$ (E(X))² (d) $\sqrt{E (X^{2}) - {(E (X))}^{2}}$

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Solution

Since, the variance of a discrete random variable X is given by:

Var(X) = E(X²) $-$ (E(X))²

Hence, the correct alternative is option (c).

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