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variance (mg86506)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86547] variance (mg86506)
  • From: Kowalczyk-Schröder <HB-Kowalczyk-Schroeders at t-online.de>
  • Date: Thu, 13 Mar 2008 04:35:07 -0500 (EST)

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>
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??
-- 
Best Wishes!
Yours Sincerely
 
Mathematica divides by (N-1) - like as far as I know all programs- This
is correct if you have only a sample and not the whole. You can look up
the reason for this and the derivation in some book about statistics.
 
Sincerely,
 J. Schroeder
############################
Dr. Joerg Schroeder
Bremen
 



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