Re: Puzzled by the "Variance"

*To*: mathgroup at smc.vnet.net*Subject*: [mg86533] Re: Puzzled by the "Variance"*From*: giovanni resta <g.restaCUT at CUTiit.cnr.it>*Date*: Thu, 13 Mar 2008 04:32:31 -0500 (EST)*References*: <fr8b97$h2s$1@smc.vnet.net>

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?? Because, as it is explained in the help page, Variance[list] is computed as Total[(list-Mean[list])^2]/(Length[list]-1) So the total is divided by (number of elements)-1 and not by (no. of elements). g.