Question

The sutton police department must write, on average, 6 tickets a day to keep department revenues at budgeted levels. suppose the number of tickets written per day follows a poisson distribution with a mean of 6.5 tickets per day. interpret the value of the mean.

Answer 1

The Poisson distribution defines the probability of k discrete and independent events occurring in a given time interval.
If λ = the average number of event occurring within the given interval, then
$P(k \, events) = e^{-\lambda } ( \frac{\lambda ^{k}}{k!} )$

For the given problem,
λ = 6.5, average number of tickets per day.
k = 6, the required number of tickets per day
The Poisson distribution is
$P(k \, tickets/day)=e^{-6.5} ( \frac{6.5 ^{k}}{k!} )$
The distribution is graphed as shown below.

Answer: 
The mean is λ = 6.5 tickets per day, and it represents the expected number of tickets written per day.
The required value of k = 6 is less than the expected value, therefore the department's revenue target is met on an average basis.