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https://issues.apache.org/jira/browse/MATH-1502?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16963481#comment-16963481
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Gilles Sadowski commented on MATH-1502:
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The attached plot shows that the {{exactP}} function drops sharply around 0.55;
this would explain why alternative implementations produce either 0.6 or 0.1
for points around that value.
> KolmogorovSmirnovTest#exactP value is incorrect in 3.6.1 potential bug
> ----------------------------------------------------------------------
>
> Key: MATH-1502
> URL: https://issues.apache.org/jira/browse/MATH-1502
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.6.1
> Reporter: Ethan Mahintorabi
> Priority: Critical
> Attachments: exact_vs_approximate.png
>
>
> I believe that I have found a bug in the calculation of the exactP value in
> KolmogorovSmirnovTest.java in version 3.6.1.
>
> In version 3.4.1 KolmogorovSmirnovTest#exactP(0.5633587786259542, 3, 3, true)
> = 0.6
>
> Where as
>
> In version 3.6.1 KolmogorovSmirnovTest#exactP(0.5633587786259542, 3, 3, true)
> = 0.09999999999999998
>
>
> The approximateP value has stayed the same at ~=0.72. This seems to
> correspond with the change in methods of calculation in
> e38bbb9f4191d0d21dea0ba31fdc131b97a5597b
>
> [https://github.com/apache/commons-math/commit/e38bbb9f4191d0d21dea0ba31fdc131b97a5597b#diff-34100572fcc8e6537bc7445a0e82b900]
>
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