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RE: st: Moderation effect by splitting the sample


From   Ebru Ozturk <ebru_0512@hotmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Moderation effect by splitting the sample
Date   Fri, 21 Dec 2012 11:03:01 +0200

The other thing is that the examples you have given is really complicated. It's very hard for me to understand what each command is doing. So is there any other way for people like me from different disciplines not from econometrics?

Kind regards
Ebru

----------------------------------------
> Date: Thu, 20 Dec 2012 20:53:17 +0100
> Subject: Re: st: Moderation effect by splitting the sample
> From: maartenlbuis@gmail.com
> To: statalist@hsphsun2.harvard.edu
>
> On Thu, Dec 20, 2012 at 8:42 PM, Ebru Ozturk wrote:
> > For non-linear models, I want to test the moderation effect of X variable. Can I test this moderation effect by spliting the sample according to X variable (moderator)?
>
> That is typically inefficient. Moderation is just an interaction
> effect. Splitting a sample means that you added an interaction term
> with all variables. This is typically not what you want, and often
> leads to a severe loss of power. It is even worse if your variable x
> is continuous and you are splitting the sample by first making it
> categorical by splitting it at some arbitrary number (e.g. the median
> from your previous question). That is a very bad idea, as you would
> loose even more information that way. Instead you should just add your
> interaction effect and interpret it correctly. Various examples are
> given here: <http://www.maartenbuis.nl/publications/interactions.html>.
>
> -- Maarten
>
> ---------------------------------
> Maarten L. Buis
> WZB
> Reichpietschufer 50
> 10785 Berlin
> Germany
>
> http://www.maartenbuis.nl
> ---------------------------------
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