Question

Choose the correct option from the given alternative:

If p.m.f. of a d.r.v. X is P (X = x) = `x^2 /(n (n + 1))`, for x = 1, 2, 3, . . ., n and = 0, otherwise then E (X ) =

Options

• `n/ 1 + 1/ 2`

• `n /3 + 1 /6`

• `n/ 2 + 1 /5`

• `n /1 + 1/ 3`

Answer 1

If p.m.f. of a d.r.v. X is P (X = x) = `x^2 /(n (n + 1))`, for x = 1, 2, 3, . . ., n and = 0, otherwise then E (X ) = `n /3 + 1 /6`