In probability theory and statistics, the Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time and/or space if these events occur with a known average rate and independently of the time since the last event.

The Poisson Distribution Calculator for iPad and iPhone provides for Data Entry for the Number of Events variable ( Range 1-48 ) and the Expected Number of Events ( Range 1-64 ). From this data the app calculates a Poisson Point Probability and a Cumulative Poisson Probability. A Graph selection visualizes the Density and Cumulative Poisson Probabilities in Poisson Probability Distribution curves.