I can't get to the answer in book.
Question: A petrol station has service areas on both sides of a motorway, one to serve east-bound traffic and the other for west-bound traffic. The number of east-bound vehicles arriving at the station in one minute has a Poisson distribution with mean 1.6, the two distributions being independent.
(i) (b) Find the probability that in a one-minute period more than two vehicles arrive at this petrol station.
My working is like this.
East bound vehicles per minute mean = 0.9
West bound vehicles per minute mean = 1.6
Let T = total vehicles per minute (ie in both directions)
T ~ Poisson(2.5)
P(T > 2) = 1 - P(0) - P(1) or 1 - P(1)cumulative
= 1 - 0.2873 = 0.713 (3 d.p.)
[0.2873]
I can't see how else you would do this question???
Book answer is 0.456.
Can any one point me in the right direction?