Poisson Probability Calculator — Formula
## How to Calculate Poisson Probability
### Formula
**P(X = k) = (lambda^k * e^(-lambda)) / k!**
The Poisson distribution models the number of events occurring in a fixed interval of time or space, when events happen independently at a constant average rate lambda. Both the mean and variance equal lambda.
### Formula
**P(X = k) = (lambda^k * e^(-lambda)) / k!**
The Poisson distribution models the number of events occurring in a fixed interval of time or space, when events happen independently at a constant average rate lambda. Both the mean and variance equal lambda.
Esempio Risolto
A call center receives an average of 4 calls per hour. What is the probability of exactly 2 calls in an hour?
- lambda = 4, k = 2
- P(X=2) = (4^2 * e^(-4)) / 2!
- = (16 * 0.01832) / 2
- = 0.29305 / 2
- = 0.14653