Poisson Distribution




The Poisson Distribution is used to model stochastic events, such as arrival times. The lambda parameter represents the average rate of arrivals per unit time. In the above equation, p(lambda,x) represents the probability that x arrivals will occur in one unit of time when the average rate of arrival is equal to lambda.



Exponential Distribution





If a number of events occur with a Poisson distribution, then the time intervals between the events are exponentially distributed. Length of a time interval can take any value, so the distribution is continuous.