.
The Poisson Distribution is another discrete probability
distribution. We will not be given a number of trials as in the
binomial distribution, nor will be given the probability of success
on a certain trial. What we will be given is the average number
of successes in a certain time period. This mean amount is called
lambda, and its symbol is .
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 
.
We will talk more a little later about how to find this probability.
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 
.