Hi
two chosen...
expected value is the SUM of nP(n) where n is 0,1,2
.....
for example
five children: 3G, 2B
Determine the expected value of the number of girls who will be selected
.........
n P(n)
0 1/10 P(both boys) =
1 3/5 P(one girl) =
2 3/10 P(two girls) =
1
......
Exp = 0(1/10) + 1(3/5) + 2(3/10) = 6/10 + 6/10 = 12/10) = 1.2 0r 1 girl