# Poisson distribution Probabilities

Calculates probabilities under Poisson distribution.

## Poisson distribution formulas

X is a random variable that counts the number of events that occur during a fixed time or space interval. We suppose that X follows a poisson distribution of parameter `lambda`.

P(X = k) is the probability of having exactly k event occurences.

`P(X = k) = (lambda^k * e^(-k))/(k!)`

where `k!` is the factorial of k,
`k! = 1*2*3...*(k-1)*k`

## See also

Inverse Poisson distribution

Measures on poisson distribution

Poisson distribution Chart

Statistics Calculators