Hi All:

This time I am asking a question. I am teaching stats next semester after several years of not doing it. I was looking through an old stats book and doing some problems. Here is a Poisson that has me stumped.

"Cars going through an intersection average 40 per hour. What is the probability that the time between the arrival of a car and the second car after it is at least 2 minutes?"

In this case, they are asking for 'at least 2 MINUTES", but the average is given in hours. So,

I was thinking maybe a gamma, like so:

but that does not seem correct.

But this would be fine if the problem said, "what is the probability that the time between arrivals of any two cars is at least two minutes.

It's the "arrival of a car and the second after that is at least two minutes" I am unsure of.

Any ideas what I am overlooking. I feel rather obtuse on this. MrF, what is my oversight/mental block?