The negative exponential (or just exponential)
distribution has only one parameter, the mean.
• It is derived from the characteristics of purely
random arrival processes.
• As a result, it is used to sample time between events,
such as the inter-arrival time of customers and the time between failure of machines.
• Note that there is a close relationship between the
negative exponential distribution and the Poisson
distribution, which can be used to sample the
number of events in an interval of time.