O RANDOM VARIABLES AND DISTRIBUTIONS Expectation and variance of a random variable D 3/5 Let X be a random variable with the following probability distribution. Value x of X P ( X=x) -30 0.05 -20 0.20 .10 0.10 0 0.05 10 0.55 20 0.05 Complete the following. (If necessary, consult a list of formulas.) (a) Find the expectation E (X ) of X. E (X) = 1 X (b) Find the variance Var(X) of X. Var (x) = 1