No. of successes: 0 1 2 3
Probability: 8/27 12/27 6/27 1/27
E(X) = 0(8/27) + 1(12/27) + 2(6/27) + 3(1/27) = 27/27 = 1;
E(X^2) = 0^2(8/27) + 1^2(12/27) + 2^2(6/27) + 3^2(1/27) = 45/27
V(X) = E(X^2) - [E(X)]^2
V(X) = 45/27 - (1)^2 = 45/27 -1 = 18/27 = 0.66