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Re: st: Moderated mediation with multilevel data


From   "Casey P. Durand" <durandca@usc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Moderated mediation with multilevel data
Date   Mon, 27 Feb 2012 17:30:23 -0800

Kris,

Due to lack of statistical power to detect moderated effects, it is
sometimes advisable to consider a higher p-value as evidence of an
interaction.  You can then move on to simple slopes analysis (aka
interaction probing), as they do in the example you cite, to more
fully explore the effect.  So the p-value for the interaction term is
in some instances just an initial, rough screening.

See:
McClelland GH, Judd CM. Statistical difficulties of detecting
interactions and moderator effects. Psychol Bull. 1993;114:376–390.

-Casey


On Mon, Feb 27, 2012 at 1:18 PM, Kris Anderson <andersok@reed.edu> wrote:
>
> Hi, all.
>
> I have been using two Stata FAQs ("How can I do moderated mediation in Stata? and "How can I perform mediation with multilevel data?").
>
> I am getting stuck on one aspect of the FAQ for moderated mediation.  In Model 3, it probes mediation at levels of the moderator but the interaction is nonsignificant in the sample output they provide. Can anyone explain that? (I contacted the authors directly without a reply). In my own data, the interaction of mw is nonsignificant, but when I run the nlcom and bootstrap the results, each level is significant.
>
> The second issue is that my data is multilevel. Does anyone know of a way to run moderated mediation in Stata with multilevel data? When I ignore the levels, I find mediation but I want to confirm it as the levels matter.
>
> Best,
> kris
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