At the recent JMP Discovery Summit, I overheard a conversation between a professor and one of the JMP developers, Clay Barker. The professor was interested in understanding tools available for generating distributions in JMP.

My first thought (although I was just a fly on the wall) was to suggest the **Distribution Calculator**, one of the interactive tools available for teaching statistical concepts.

But, Clay had another suggestion, which caught me off guard (mostly because I wasn’t aware that it existed). Clay showed the professor the **Probability Functions in the Scripting Index** (under the help menu). This function group provides JSL code to generate density functions for a number of popular distributions. Simply select the desired density function, and click Run Example.

Then, click and drag the slider(s) to see how the shape of the distribution changes as the parameter(s) of the distribution change – use your hand tool to adjust the axes as needed.

You can also use the probability functions to quickly calculate quantiles (or percentiles) for selected distributions. For example, for the standard normal distribution, the 0.9 quantile (or 90^{th} percentile) is 1.2815. Looking for a different quantile? Simply change the value in the example script provided, and click Run Example.

Sometimes it pays to be a fly on the wall – you never know what you’ll learn (especially if you’re lucky enough to spend any time with our developers)!

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