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Id: 37109
Status: new
Priority: 0/
Queue: Statistics-TTest

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Owner: Nobody in particular
Requestors: b.e.buck [...] clearwire.net
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CC: bug-Statistics-ttest [...] rt.cpan.org
Subject: Divide by zero in fdist module
Date: Wed, 25 Jun 2008 16:27:10 -0400
To: bug-Statistics-Distributions [...] rt.cpan.org
From: b.e.buck [...] clearwire.net
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line 325/326 sub _subf2 has data vulnerabilities when called from t-test. It can wind up trying to take log's of negative numbers or dividing by zero if $n (the sample size) is sufficiently large that ($n - 2) * log($x) winds up being very negative, resulting in an exponent of a negative number. $x is frequently negative such that this can happen easily for large $n. Module 1.02 of Statistics::Distributions PERL 5.84 A trivial fix is to return $x = 1 for $z=>0 and $x = 0 for $x=>negative, but that may not be the desired behavior. You'd have to be much better at statistics and understanding what this part of the f-test calculation is actually *doing* to know if that's the right behavior. Thanks for any help on this, -- Ben


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