# Possson Probablilty

1. Oct 22, 2011

### nathangrand

Cars pass at randoms times at an average rate of one a minute. The chance of a car stopping to give you a lift is one percent. What is the probability you will have got a lift within one hour?

This has pretty much stumped me. I know λ=60 as expecting 60 cars an hour for the poisson distribution but there's a binomial aspect to this as well because of each car either giving you a lift or not giving you a lift

2. Oct 22, 2011

### vela

Staff Emeritus
It's probably easiest to calculate the probability you don't get a ride and then subtract that from 1.

3. Oct 23, 2011

### nathangrand

I agree! But how?

4. Oct 23, 2011

### vela

Staff Emeritus
What's the probability that exactly n cars pass in an hour?

5. Oct 23, 2011

### Ray Vickson

If N is the number of cars passing in time t, the event E = {no ride in time t} consists of {N=0} or {N=1 & no ride} or {N=2 & no ride} or .... . Are you familiar with the exponential series? If not, see http://en.wikipedia.org/wiki/Exponential_function .

RGV