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title: "Cumulative percentiles"
canonical: "https://modelassist.epixanalytics.com/space/EA/26575491/Cumulative%20percentiles"
format: markdown
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These are values below which a specified percent of the generated data for an output fall.  Standard notation is for the P<sup>th</sup> percentile is *x*<sub>P</sub> e.g. *x*<sub>75</sub> is the value we estimate from the model to have a 75% probability of being below.

  


Differences between cumulative percentiles are often used as a measure of the variable's range e.g. x<sub>95</sub> - *x*<sub>05</sub> would include the middle 90% of the possible output values and *x*<sub>80</sub> - *x*<sub>20</sub> would include the middle 60% of the possible values of the output. *x*<sub>25</sub>, *x*<sub>50</sub> and *x*<sub>75</sub> are sometimes referred to as the *quartiles*.

  


The median is the 50th percentile and a stable measure of location. The easiest way to illustrate and present cumulative percentiles is to quote the most interesting percentiles in combination with showing them on a [cumulative distribution plot](https://epixanalytics.atlassian.net/wiki/spaces/EA/pages/26575476/).

  


  


  


  


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