Fundamentals of Statistics contains material of various lectures and courses of H. Lohninger on statistics, data analysis and here for more.

Poisson Distribution


Similar to binomial distribution, but used if the probability that the observed event occurs is very small, in contrast to the population, that is a very large number. 

Graphic Representation
Applications The Poisson distribution is the distribution of rare events. A typical application is the probability that a certain number of accidents will occur in a given interval, or the probability of radioactive decay. The number of atoms to decompose is relatively small compared to the number of all atoms in the material. 
Mean μ = λ
Variance σ = λ
Simulation The program Discrete Distributions calculates the probability density functions of the binomial, the hypergeometric, and Poisson distribution. After specifying the appropriate parameters both the probability density and the cumulative distribution is calculated and displayed.