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Re: Puzzled by the "Variance"

• To: mathgroup at smc.vnet.net
• Subject: [mg86512] Re: Puzzled by the "Variance"
• From: "Solomon, Joshua" <J.A.Solomon at city.ac.uk>
• Date: Thu, 13 Mar 2008 04:28:34 -0500 (EST)
• References: <fr8b97$h2s$1@smc.vnet.net>

for sample variance, you want to divide by N-1, not N.
j

On 12/03/2008 10:28, in article fr8b97$h2s$1 at smc.vnet.net, "Elements"
<philyer at gmail.com> wrote:

> Greeting all
> I'm puzzled by the function "Variance". We can learn how to calculate
> variance from this page:http://mathworld.wolfram.com/SampleVariance.html.
> 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??