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MathGroup Archive 2004

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Re: Variance of sample and whole dataset

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51210] Re: Variance of sample and whole dataset
  • From: "Steve Luttrell" <steve_usenet at _removemefirst_luttrell.org.uk>
  • Date: Fri, 8 Oct 2004 02:55:07 -0400 (EDT)
  • References: <ck340j$b1j$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

You can define a variance function thus:

var[dataset_]:=(Apply[Plus,#^2]/Length[#]-(Apply[Plus,#]/Length[#])^2)&[dataset];

and use it as in this example:

dataset={a,b,c};
var[dataset]

giving

(-(1/9))*(a + b + c)^2 + (1/3)*(a^2 + b^2 + c^2)

Steve Luttrell

"Uwe Ziegenhagen" <newsgroup at ziegenhagen.info> wrote in message 
news:ck340j$b1j$1 at smc.vnet.net...
> Hello,
>
> with Variance[list] and StandardDeviation[list] I get the
> variance/std.dev for samples.
>
> Is there any builtin command for the variance of whole dataset (division
> by n, not by n-1)?
>
> Uwe
>
>
> -- 
>
> mail to newsgroup at ziegenhagen.info is read only from time to time. If
> you need an urgent answer, google for me.
> 



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