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)

Answer 1

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`