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title: "JohnsonB"
canonical: "https://modelassist.epixanalytics.com/space/EA/26575237/JohnsonB"
format: markdown
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No CrystalBall function

JohnsonB(*a*1, *a*2, Min, Max)

[JohnsonB equations](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26576228)

 

![image](media://31d7027f-4587-4c66-b0fd-2a64f7572f05)

 

The Johnson bounded distribution has a range defined by the Min and Max parameters. Combined with its flexibility in shape, this makes it a viable alternative to the [PERT](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26576387), [Triangular](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26576437) and [Uniform](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26575256) distributions for [modeling expert opinion](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26575440). 

Setting Min to 0 and Max to 1 gives a random variable that is sometimes used to model ratios, probabilities, etc instead of a Beta distribution.

The distribution name comes from [Johnson (1949)](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26579303) who proposed a system for categorizing distributions, in much the same spirit that [Pearson did](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26575249). Johnson's idea was to translate distributions to be a function of a unit Normal distribution, one of the few distributions for which there were good tools available at the time to handle.

 

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