Simulation software offer a wide variety of probability distributions that cover most common risk analysis problems. However, one might occasionally wish to generate one's own probability distribution. There are several reasons why one would prefer to make one's own distribution, and there are four main ways to do this. The choice of which method to use will be determined by the following criteria:

 

 

In addition to creating your own distributions sometimes it is very useful to approximate a distribution with another one which is discussed in the following section.