Overview
The Erlang distribution is a series of k exponential distributions all with rate . The hypoexponential is a series of k exponential distributions each with their own rate, the rate of the exponential distribution. If we have k independently distributed exponential random variables, then the random variable,
is hypoexponentially distributed. The hypoexponential has a minimum coefficient of variation of .
Read more about this topic: Hypoexponential Distribution