Re: st: Re: RE: when your sample is the entire population

["Michael Blasnik" <michael.blasnik@verizon.net>]

Absolutely -- that issue is often the major issue in program evaluations.  I 
hope I didn't imply anything else.

Michael

----- Original Message ----- 
From: "David Greenberg" <dg4@nyu.edu>
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, January 18, 2008 7:08 PM
Subject: Re: st: Re: RE: when your sample is the entire population



> Michael, while it is true that program participants or school children could 
> be considered a sample of a larger population, people are not usually in 
> treatment programs or in particular schools at random, and the choice of 
> institutions to study -  this school rather than that school - are often not 
> made at random either. So, one may have a sample but ordinarily not a simple 
> random sample. Without taking selection effects into account, generalization 
> to a larger population could be quite treacherous. David Greenberg, Sociology 
> Department, New York University
>
> ----- Original Message -----
> From: Michael Blasnik <michael.blasnik@verizon.net>
> Date: Friday, January 18, 2008 4:32 pm
> Subject: st: Re: RE: when your sample is the entire population
> To: statalist@hsphsun2.harvard.edu
>
>
>
> > I would just say -- "what Nick says" ;)
> >
> > But I'd like to emphasize one aspect related to his points 3 (and/or
> > 4) --
> > measurement error.  In many real applications, the outcome (and,
> > unfortunately,
> > the predictors) are measured with error.  Therefore, you have
> > uncertainty even
> > with data for the full population.  Also, the superpopulation concept
> > ( point 1)
> > seems quite reasonable -- at least for most program evaluation
> > questions where
> > you may collect data for all program participants (or kids in a
> > school) but they
> > can be considered a sample of some larger potential population.  Of
> > course in
> > program evaluation you also still have uncertainty introduced by any
> > comparison/control group employed in the analysis.
> >
> > Michael Blasnik
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