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| From | Tim Scharks <tim.scharks@gmail.com> |
| To | statalist@hsphsun2.harvard.edu |
| Subject | Re: st: Average of Sample vesus Sub-Samples |
| Date | Fri, 19 Mar 2010 08:24:12 -0700 |
but what about A = 1, 1, 1 B = 3 m(A) = 1 m(B) = 3 (m(A)+m(B))/2=2 mean (A+B) =1.5 uh oh... The problem is not negative numbers--it is your failure to weight the subsample means according to their relative size: (m(A)*3+m(B)*1)/4 =1.5 m(A+B) = 1.5 On Fri, Mar 19, 2010 at 6:49 AM, Jeph Herrin <junk@spandrel.net> wrote: > Yes, if they are negative. > > > A = -1,-1,-1 > B = -3 > then > mean(A) = -1 > mean(B) = -3 > (mean(A)+mean(B))/2 = -2 > mean(A+B)= -6/4 = -1.5 > > -1.5 > -2 > > So the average of all 4 numbers is larger than > the average of the means of the two subsamples. > > > hth, > Jeph > > > > > > Erasmo Giambona wrote: >> >> Dear Statalisters, >> >> Is it possible that the arithmetic average of a sample is larger than >> the averages of two sub-samples containing overall all the >> observations of the full samples? >> >> Any thoughts would be appreciated, >> >> Erasmo >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/statalist/faq >> * http://www.ats.ucla.edu/stat/stata/ >> > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/