Question

Suppose a ball is drawn at random box containing three white and three black balls. After a ball is drawn, it is then replaced and another is drawn. What is the probability that the first four balls drawn, exactly two are white.

Answer 1

This is a binomial distribution with $n=4, \;p=0.5.$

$P(X=2)=C_4^20.5^20.5^2=6*0.25*0.25=0.375.$