Just as with the binomial distribution there is a formula for
calculating probabilities using the Poisson distribution. Here
it is.
Now to apply it to the problems already mentioned.
Ex. On an average Friday, a waitress gets no tip from 5 customers.
Find the probability that she will get no tip from 7 customers
this Friday.
The waitress averages 5 customers that leave no tip on Fridays
: 
= 5.
Random Variable : The number of customers that leave her no tip this Friday.
We are interested in 
.
So, the probability that 7 customers will leave no tip this Friday is 0.1044.
(Be kind to your waitress and drive carefully! Good night!)
Ex. During a typical football game, a coach can expect 3.2 injuries.
Find the probability that the team will have at most 1 injury
in this game.
A coach can expect 3.2 injuries : 
= 3.2.
Random Variable : The number of injuries the team has in this game.
We are interested in 
.
