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From "Sriram Natarajan (JIRA)" <>
Subject [jira] [Commented] (MATH-1185) Tail probability drops to zero beyond 10e-17 ?
Date Mon, 05 Jan 2015 22:41:35 GMT


Sriram Natarajan commented on MATH-1185:

Appreciate all the comments regarding precision vs. absolute magnitude. Thanks for your work
on this project and responding to a newcomer who is using commons-math for the first time
(from Scala).

Yes, I was wrong about the stock functions in R.  Excel does report small values.  In the
mid-90s, I recall there being a stat lib called dcdflib ported from Fortran to C  that was
able to report these small numbers (A lot of magic numbers taken from Abramowitz and Stegun
were in the source). Apparently it is still there:
linked from

> Tail probability drops to zero beyond 10e-17 ?
> ----------------------------------------------
>                 Key: MATH-1185
>                 URL:
>             Project: Commons Math
>          Issue Type: Wish
>    Affects Versions: 3.3, 3.4
>            Reporter: Sriram Natarajan
>            Priority: Minor
> This could be a  simple question, In which case I can expect a clarification. If this
is the wrong place to post such a question, let me know.
> OS: Windows 8.1, Java 1.8.0_25
> ChiSquaredDistribution chisq = new ChiSquaredDistribution(23)
> 1.0 - chisq.cumulativeProbability(130) is  1.1102230246251565E-16
> 1.0 - chisq.cumulativeProbability(131) is  0.0  
> Am pretty sure it is not a formatting issue.  Is there a reason why the tail drops to
zero at this point?

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