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From "Phil Steitz" <>
Subject Re: Commons.Math.Distrubition
Date Sat, 29 Sep 2007 19:25:56 GMT
On 9/29/07, Amnon Lahav <> wrote:
> Hi ,
> how is the Standard deviation calculated in the commons math ? because i'm
> getting diffrent values then my code which i used till far , iswtiched out
> of runtime speed considerations and i know my code is OK since it mathces
> the stock exchange's values ...
> isn't is for 20days periods  ?
> thanks .

The exact computation depends on whether you supply the whole array of
values or feed them in one at a time; though for small arrays the
results should not differ.  See
for a description of the computational formulas used.  Math.sqrt is
used to get the standard deviation from the variance.

What class / method are you using?  Can you share the data and
expected results?  If so and you can't explain the difference, please
open a Jira ticket here.


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