Re: Puzzled by the "Variance"
- To: mathgroup at smc.vnet.net
- Subject: [mg86520] Re: Puzzled by the "Variance"
- From: "Kevin J. McCann" <Kevin.McCann at umbc.edu>
- Date: Thu, 13 Mar 2008 04:30:04 -0500 (EST)
- Organization: University System of Maryland
- References: <fr8b97$h2s$1@smc.vnet.net>
The answer is, I believe, in the article you quote. The gist of it is that you divide by (n-1) not n for an unbiased estimator of the variance. To see that Mathematica is actually doing this, I commend to you the Help on Variance. Kevin Elements 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?? -- Kevin J. McCann Research Associate Professor JCET/Physics Physics Building University of Maryland, Baltimore County 1000 Hilltop Circle Baltimore, MD 21250