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>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, you are shure that varance is not Sum[x[i]-Mean[x],{i,n}]/(n-1) ? and your example should be ((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 > 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??