Re: st: Finite population correction when testing equality of two proportions

[Fredrik Nyberg <fredrik.nyberg@imm.ki.se>]

I think what you describe is appropriate if we assume that the whole
population (overall sample) is a random sample of a larger population and is
composed of two groups (eg male/female) that are then likewise random
samples of the larger population.

This is not the same test that I seek.

Consider an overall population of 1000 subjects, with 50% males. If I take
one subsample of 10 subjects with 9 males (90% males) and compare with the
remaining 990 (still ~50%), the proportions are significantly different, but
obviously my second subsample of 990 is not significantly different from 
the full 1000
(both ~50%).

Any other suggestions on how to perform this latter test (the 990 to the full
1000 = sample 2 to sample 1 in the terminology of my initial question) in a 
simple/convenient way?

Fredrik

At 2005-04-01 22:06, Richard Williams wrote:

> At 09:41 PM 4/1/2005 +0200, Fredrik Nyberg wrote:
> > Hi all Statalisters
> >
> > I am wondering about testing two proportions in the following setting:
> > Infinite overall population size (for all practical purposes)
> > Sample 1 taken from overall population
> > Sample 2 subsampled from sample 1
> >
> > Since these are not two independent samples from the same overall 
> > population, I think I need to adjust the test by making a finite 
> > population correction somehow for sampling sample 2 from sample 1. Only I 
> > can't find any details on this nor a test that appears suitable in Stata.
> >
> > Can anyone help?
> > What is the correct test?
> > Is there Stata-code available?
> My initial inclination is to go to sample 1 and code each case as 1 if not 
> in sample 2, 2 if in sample 2.  Then, use the -prtest- command to compare 
> the 2 groups.  But, my initial inclinations have been wrong before.  The 
> -prtest- command is discussed on the last page of this handout:
>
> http://www.nd.edu/~rwilliam/xsoc592/lectures/TwoSample-Stata.pdf
>
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