Re: Puzzled by the "Variance"

• To: mathgroup at smc.vnet.net
• Subject: [mg86524] Re: Puzzled by the "Variance"
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Thu, 13 Mar 2008 04:30:48 -0500 (EST)
• Organization: Uni Leipzig
• References: <fr8b97\$h2s\$1@smc.vnet.net>

```Hi,

you are shure that varance is not

Sum[x[i]-Mean[x],{i,n}]/(n-1)

?

((1-2)^2+(2-2)^2+(3-2)^2)/2 -> 1

??

And any text book about statistics can tell you "Why?"
there is the factor 1/(n-1) and not 1/n.

Regards
Jens

Elements wrote:
> Greeting all
> I'm puzzled by the function "Variance". We can learn how to calculate
> For example, calculate the sample variance of {1,2,3}. the average of
> {1,2,3} is 2, then the variance should be ((1-2)^2+(2-2)^2+(3-2)^2)/3=2/3.
> But mathematica gives that:
>
> In[10]:= Variance[{1.0,2.0,3.0}]
> Out[10]= 1.
>
> Why??

```

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