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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-2494) Stat calculation of STDEV may be inaccurate
Date Tue, 25 Mar 2014 14:45:23 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-2494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13946629#comment-13946629
] 

Mike Drob commented on ACCUMULO-2494:
-------------------------------------

[~elserj] - No, my next question was going to be how this ever worked, since I thought we
already had a dependency on commons-math and that's why this change was safe to include. However,
we only had it in the parent dependency management section, and an explicit dependency under
test, so I'm not sure how this even compiled on my machine. Probably a transitive dependency
somewhere...

Looks like [~ecn] beat me to adding it to the pom, but I'll verify the tarball and generated
RPMs/DEBs as well.

> Stat calculation of STDEV may be inaccurate
> -------------------------------------------
>
>                 Key: ACCUMULO-2494
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-2494
>             Project: Accumulo
>          Issue Type: Bug
>          Components: client
>            Reporter: Mike Drob
>            Assignee: Mike Drob
>             Fix For: 1.5.2, 1.6.0
>
>
> The math is sound, but it is susceptible to rounding errors. We should address that.
> See http://www.strchr.com/standard_deviation_in_one_pass and http://www.cs.berkeley.edu/~mhoemmen/cs194/Tutorials/variance.pdf



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