Question
Question: In a P.D., E(x<sup>2</sup>)= 20, P(X=1) = ............
In a P.D., E(x2)= 20, P(X=1) = .........
A
2/e2
B
3/e2
C
4/e4
D
6/e4
Answer
4/e4
Explanation
Solution
V(x) + [E(x)]2 = 20
λ + λ2= 20
λ2 + λ - 20 = 0
(λ +5) (λ-4) = 0
λ = 4
P(X=1) = λe-λ = 4e-4 = e44 .