Calculate the mean value for the number of heads appearing in a simultaneous throw of 3 coins.
The outcomes are
X={0,1,2,3}, with probabilities
P(x)=(1/8)x!/(3!(3-x)!)
The mean, or expected value
E[X]=ΣxP(x)
=Σ(0*(1/8)+1*(3/8)+2*(3/8)+3*(1/8))
=12/8
=3/2