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merging and sample size [was: Re: st: Re: ESTIMATING THE LA/AIDS MODEL]


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   merging and sample size [was: Re: st: Re: ESTIMATING THE LA/AIDS MODEL]
Date   Wed, 13 Jun 2012 14:40:00 +0200

On Wed, Jun 13, 2012 at 2:27 PM, daniel milandu  wrote:
> after merging data sets is my sample size supposed to increase

That can happen when the "using dataset" (the dataset you specified
after -using-) contains observations form which no match was found in
the master dataset (the dataset that was open when you called
-merge-). After merging you can see where each observation comes from
(i.e. both datasets, only the master, or only  the using dataset) by
looking at the variable _merge. You can than decide whether this
represents a problem or that you can safely drop (some) unmatched
observations.

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany


http://www.maartenbuis.nl
--------------------------
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