Re: Puzzled by the "Variance"

*To*: mathgroup at smc.vnet.net*Subject*: [mg86537] Re: [mg86506] Puzzled by the "Variance"*From*: DrMajorBob <drmajorbob at bigfoot.com>*Date*: Thu, 13 Mar 2008 04:33:15 -0500 (EST)*References*: <31283773.1205350347270.JavaMail.root@m08>*Reply-to*: drmajorbob at longhorns.com

Variance gives the "unbiased estimate" of true variance based on a sampl= e: test = {1, 2, 3} Variance@test {1, 2, 3} 1 biased[x_List] := #.# &[x - Mean@x]/Length@test biased@test 2/3 or... biased[x_List] := (Length@x - 1)/Length@x Variance@x biased@test 2/3 Bobby On Wed, 12 Mar 2008 05:29:07 -0500, 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.ht= ml. > 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?? -- = DrMajorBob at longhorns.com