Poisson Distribution Function

JavaScript

      Enter Poisson Distribution Arguments

          x-value: 
           λ:

Poisson P(X<=x|λ) :

If items arrive at times 0< t₁ < t₂ < ... such that the interarrival times,
t₁, t₂-t₁, t₃-t₂, ... are independent with exponential distributions, E(1),
then the number of arrivals that occur in the time interval (0,λ)
has the Poisson distribution, P(λ). This distribution has mean
λ, variance λ, and probability mass function,

f(x | λ) = e^-λ λ^x/x! for x = 0,1,2,...

For the distribution function, we have as an example,
P(x<=1| 1) = 1/e + 1/e = .73576