Suppose that previously collected traffic data indicated that, during the afternoon rush hour, an average of 4 cars arrive at a toll bridge each second. If it is assumed that the cars arrive randomly, and can thus be modeled with a Poisson distribution, what is the probability that in the next second, NO cars will arrive. Solution lambda = mean number of cars crossing bridge each second = 4 probability that no cars arrive in next second = P(X=0) = 4^0/0! * e^-4 = 0.0183.

1. Suppose that previously collected traffic data indicated that, during the afternoon rush hour, an
average of 4 cars arrive at a toll bridge each second. If it is assumed that the cars arrive
randomly, and can thus be modeled with a Poisson distribution, what is the probability that in the
next second, NO cars will arrive.
Solution
lambda = mean number of cars crossing bridge each second
= 4
probability that no cars arrive in next second
= P(X=0)
= 4^0/0! * e^-4
= 0.0183