"Poisson Distribution"
Poisson distribution
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The Poisson Distribution describes the probability of a particular number of discrete events occurring within a fixed period of time if these events occur with a known average rate, independently of the time since the last event.

P(x; μ) = (e^-μ) (μ^x) / x!

where the average rate is μ and the actual number of events is x.


The distribution was first introduced by Simeon Denis Poisson in 1838.