Question

Each child born to a particular set of parents has probability 0.25 of having blood type o. if these parents have 5 children, what is the probability that exactly 2 of them have type o blood?

Answer 1

Use binomial distribution with p=0.25, n=5, x=2
P(X=x)=C(n,x)p^x (1-p)^(n-x)

P(X=2)=C(5,2) 0.25^2 0.75^(5-2)
=10*0.0625*0.421875
=0.26367

So the probability of 2 of 5 children having type-O blood from these parents is 0.26367.