On a Test for Equality of the Means of Two Independent Poisson Distributions

In this paper, an exact method is studied for testing the equality of means of two independent Poisson distributions. The method allows for sampling over different time durations and thus, one can compare the mean time between failures of an equipment, by observing it for, say, a month, to the MTBF of another equipment which has been under observation for say six months. The purpose of the test for a given situation is discussed, and examples are given which illustrate the usefulness of the test. Extensive tables and graphs are included for those readers who wish to utilize the results.