The gamma distribution is continuous. It applies to a wide range of physical quantities and is related to other distributions: lognormal, exponential, Pascal, Erlang, Poisson, and chi-squared. It is used in meteorological processes to represent pollutant concentrations and precipitation quantities. The gamma distribution is also used to measure the time between the occurrence of events when the event process is not completely random. Other applications of the gamma distribution include inventory control (such as the demand for an expected number of units sold during the lead time), economics theory, and insurance risk theory.
The gamma distribution is used under these conditions: