Calculate Poisson probabilities
The Poisson test
compares a count of objects or
subjects (such as the number of
cars or people) in a specified
domain (for example a street
during a certain period) with
an expected number. The Poisson
test can be used as an
alternative to the Binomial
distribution in the case of
very large samples. Also, the
Poisson test can be used to
study how the chances of
observing none, one, two or
more 'accidents' or 'malfunctions'
in the domain are distributed.