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title: "Inter-percentile range"
canonical: "https://modelassist.epixanalytics.com/space/EA/26575504/Inter-percentile%20range"
format: markdown
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The inter-percentile range of an output is calculated as the difference between two percentiles, for example:

 

x<sub>95</sub>-x<sub>05</sub> to give the central 90% range

x<sub>90</sub> – minimum to give the lower 90% range

x<sub>90</sub> – x<sub>10</sub> to give the central 80% range

 

The inter-percentile range is a stable measure of spread (unless one of the percentiles is the minimum or maximum), meaning that the value is quickly obtained for relatively few iterations of a model. It also has the great advantage of having a consistent interpretation between distributions.

 

One potential problem you should be aware of is with applying an inter-percentile range calculation to a discrete distribution, particularly when there are only a few important values:

 

![image](media://8c3f1b93-25a9-4527-92b0-4cfe0484a372)

![image](media://89eebf46-d9e0-4e70-9310-735342e7ee73)

In this example, several key cumulative percentiles fall on the same values, so of course several different inter-percentile ranges take the same values. In addition, the inter-percentile range becomes very sensitive to the percentile chosen. In the plot above, for example:

 

x<sub>95</sub> – x<sub>05</sub> = 4 – 1 = 3, but

x<sub>96</sub> – x<sub>04</sub> = 5 – 0 = 5.

 

 

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