Question

Given X ~ B(n, P) if n = 10, E(X) = 8, find Var(X).

Answer 1

Given: n = 10, E(X) = 8

E(X) = np

∴ 8 = 10p

∴ p = `8/10 = 4/5`

∴ q = 1 - p = `1 - 4/5 = 1/5`

Var(X) = npq

`= 10 xx 4/5 xx 1/5 = 8/5`

Hence, Var(X) = `8/5`