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Question
The probability mass function (p.m.f.) of X is given below:
| X=x | 1 | 2 | 3 |
| P (X= x) | 1/5 | 2/5 | 2/5 |
find E(X2)
Solution
| x | P(x) | xP(x) | x2P(x) |
| 1 | 1/5 | 1/5 | 1/5 |
| 2 | 2/5 | 4/5 | 8/5 |
| 3 | 2/5 | 6/5 | 18/5 |
|
`sumx^2P(x)=27/5` |
`E(x^2)=sum x^2P(x)=27/5`
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