statistics
posted by Michael .
Suppose that the number of accidents occurring in an industrial plant is described by a Poisson process with an average of 1.5 accidents every three months. During the last three months, four accidents occurred.
(a)probability that no more than 12 accidents will occur during a particular year.
(b)probability that no accidents will occur during a particular year.

the mean is based off of 3 months. multiply it out to get the mean for a correct time period (1.5x4=6). I use the Poisson function in excel. Mean is equal to 6 and x is equal to 12 and 0. True is up to a certain number (up to 12) and false is exactly a certain number (exactly 0). In this case the answers are .9912 and .0025. Good luck