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Re: st: AW: sample size


From   Nirina F <fstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: AW: sample size
Date   Tue, 29 Sep 2009 10:53:03 -0400

Hi Martin,
Thank yu very much for your response.
The explanation was to have the same sample size as in ivreg2 but the
very good explanation outside of that on why I would do that, I myself
am not too sure....
any thought anyone?
thanks,
Nirina

On Tue, Sep 29, 2009 at 8:48 AM, Martin Weiss <martin.weiss1@gmx.de> wrote:
>
> <>
>
>
>
> This question is not so much about the size of the sample than about the
> members that are or are not included by -ivreg2-: If it was all about the
> size, you could simply say -in 1/2122- and be done...
>
> By conditioning on -e(sample)- from the -ivreg2- estimation, you tell
> -regress- to use the observations that -ivreg2- chose to use for whatever
> reasons, and you would need a very good explanation for that...
>
> You could make -e(sample)- permanent by saying something like -gen byte
> inivreg=e(sample)- and then -summarize- or -inspect- the resulting dummy to
> look for patterns that promote or discourage inclusion...
>
>
>
> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Nirina F
> Gesendet: Dienstag, 29. September 2009 14:36
> An: statalist@hsphsun2.harvard.edu
> Betreff: st: sample size
>
> hello all,
>
> When I run ivreg2, my sample size dropped from 2445 to 2122.
> What is the logic behind this sample drop?
> Also, I restricted the plain reg with if e(sample) so that I have now
> 2122 in my OLS but is it ok to do that? I mean what is the meaning
> econometrically of restricting the sample size to be the same?
>
> Thank you in advance fo rtaking the time to respond.
> Nirin
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