C(n,k) * p(e)^k * (1 - p(e))^(n-k)
where p(e) is the probability of event e. C(n,k) is the binomial formula
note to kathy, the binomial formula. 2 explanations. n things take k. or, possible arrangement of n red ball and k blue ball.
expected value. In probability theory, the expected value (aka mean, average) is a generalization of the weighted average. Informally, the expected value is the arithmetic mean of a large number of independently selected outcomes of a random variable. Expected value
Limit[ X[i]/n , {i, 1,n}] == E[X]
expected value = (num of draw) * (average)