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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`
Solution
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`
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