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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MATH-1140) Incorrect result from MannWhitneyUTest#mannWhitneyUTest with large datasets
Date Fri, 08 Aug 2014 17:39:12 GMT

     [ https://issues.apache.org/jira/browse/MATH-1140?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Gilles resolved MATH-1140.
--------------------------

    Resolution: Not a Problem

> Incorrect result from MannWhitneyUTest#mannWhitneyUTest with large datasets
> ---------------------------------------------------------------------------
>
>                 Key: MATH-1140
>                 URL: https://issues.apache.org/jira/browse/MATH-1140
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.3
>            Reporter: Anders Conbere
>            Priority: Minor
>
> On large datasets MannWhitneyUTest#mannWhitneyUTest returns the double value 0.0 instead
of the correct p-value. I suspect this is an overflow but haven't been able to trace it down
yet.
> I'm afraid I'm not very good at java, but I'm including a link to a public repository
where you can reproduce the issue, unfortunately my implementation is written in clojure.
> https://github.com/aconbere/apache-commons-mann-whitney-bug
> The summary is that by calling MannWhitneyUTest#mannWhitneyUTest with two randomly generated
arrays (50k elements with a max value of 300) I can reliably reproduce the result 0.0. By
reducing that to something more modest  like 2k I get correct p-value calculations.



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