1. ## poisson probability distribution

Im not quite sure about this can someone please give me a hint? Cars arriving for gasoline at a shell station follow a poisson distribution with a mean of 5 per hour. what is the probability that over the next hour only one car will arrive.

2. Originally Posted by jobear
Im not quite sure about this can someone please give me a hint? Cars arriving for gasoline at a shell station follow a poisson distribution with a mean of 5 per hour. what is the probability that over the next hour only one car will arrive.
Let X be the random variable number of cars arriving in one hour.

Substitute $\displaystyle \mu = 5$ into the Poisson formula:

$\displaystyle \Pr(X = x) = \frac{e^{-5} \, 5^x}{x!}$.

You want Pr(X = 1).