The department of Motor Vehicles sees 2 customers arriving for assistance every half-hour, on average. Find the probability that more than 4 customers will arrive for assistance any given half- hour increment. Solution Use Poisson distribution P(x=k)= e^-() ^k/k! Here =2 So we have k=0 P= 0.1353 k=1 P= 0.2707 k=2 P= 0.2707 k=3 P=0.1804 k=4 P= 0.0902 So more than 4 is 1 minus the above probabilities or 0.0527.