Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: st: Average of Sample vesus Sub-Samples
From
Tim Scharks <[email protected]>
To
[email protected]
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 <[email protected]> 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/