PsiPoisson (λ,...)
PsiPoisson (λ) is a discrete distribution of the number of events that occur in an interval of time, when the events occur at a known average rate, and each occurrence is independent of the time of occurrence of the previous event.
The Poisson distribution with parameter λ can be approximated by a Normal distribution with mean λ and variance λ, for large values of λ. If X1, X2,…,Xn are independent Poisson random variables with parameters λ1, λ2,… λn, then their sum is also a Poisson random variable with parameter λ1 +λ2+…+λn.
