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Re: [Help-gsl] Covariance calculation in gsl


From: Ralph Silva
Subject: Re: [Help-gsl] Covariance calculation in gsl
Date: Thu, 13 May 2010 17:00:57 +1000

It is correct.

Check for unbiasedness on the web: (e.g.
http://en.wikipedia.org/wiki/Unbiasedness)


On Thu, May 13, 2010 at 4:35 PM, Srimal Jayawardena <address@hidden>wrote:

> Hi
>
> I'm not an expert in statistics but I just realised that in the
> covariance definition used for
>
> double gsl_stats_covariance (const double data1[], const size_t
> stride1, const double data2[], const size_t stride2, const size_t n)
>
> http://www.gnu.org/software/gsl/manual/html_node/Covariance.html
>
>          covar = (1/(n - 1)) \sum_{i = 1}^{n} (x_i - \Hat x) (y_i - \Hat y)
>
> Is there any particular reason for dividing with (n-1) instead of just 'n'
> ?
>
> Whats the reasoning behind this ?
>
> Thanks in advance
>
> Srimal.
>
> --
> ~
> Srimal Jayawardena
> BSc (Engineering), BIT, MIET
> PhD Candidate
> Research School of Information Sciences and Engineering
> College of Engineering and Computer Science
> Building 115, Corner of North and Daley Roads
> Australian National University
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>
> ANU Contact Info : http://arp.anu.edu.au/user/3788
>
> http://srimal.sri-lankan.net/
> http://srimal-techdiary.blogspot.com/
>
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