The Gamma distribution is similar to a Log-Normal, but is less positively-skewed. Because it mathematically represents the time required for the occurrence of a specified number of Poisson events, it is often used to represent the time required to complete a particular task or reach a particular milestone. It is defined by a Mean and a Standard Deviation:
If desired, a Gamma distribution can be Truncated, in which case you must specify a Minimum and Maximum value. Note that in this case, the Mean and Standard Deviation inputs refer to the statistics prior to truncation.
Note: If the Mean and Standard Deviation
are identical, the Gamma distribution collapses to an exponential
distribution.