Question

A random variable X has E(x) = 2 and E(x²) = 8 its variance is
(a) 4
(b) 6
(c) 8
(d) 2

Answer 1

we have to use the formula , Var(X) = E(X²) - {E(x)}²
Here, Var(X) indicates variance of random variable
E(X) is the expectation of the expected value of X
Similarly, E(X²) is the expectation of the expected value of X²

Given,
E(X) = 2
E(X²) = 8
∴ var(X) = E(X²) - {E(X)}²
Var(X) = 8 - 2² = 8 - 4 = 4

Hence, option (a) is correct.