Hi,
POISSON Distribution P(x; μ) = (e^(-μ) (μ^x) / x! where μ is the average number of successes
x is the actual number of successes that result from the experiment, e approximately equal to 2.71828.
for ex: μ = 15 P(x = 7) = 
Recommend using Your TI calculator for cumulative probabilities.
and stattrek.com as an excellent reference.
On an assembly line an average of 15 products are boxed every minute.
In any randomly chosen minute, what is the probability that:
a. More than 7 products are boxed? P(x>7) = 1- poissioncdf(15, 7)
b. Less than 8 products are boxed? P(x< 8) = poissioncdf(15, 7)