[R] Problems on testing moderating effect (or interactive effect).

Guo Wei-Wei wwguocn at gmail.com
Wed Jul 5 03:12:15 CEST 2006

Thank you Jonathan.
I do need to read R documentation. The extra problem is time ....
Thank you for your reply.

2006/7/4, Jonathan Baron <baron at psych.upenn.edu>:
> On 07/04/06 19:51, Guo Wei-Wei wrote:
> > Can I use the variance-covariance matrix as the input data? Just like
> > what SEM does. My mentor told me to avoid sperate the operation into
> > two step, that is to get the factors' means first and then to test the
> > relationships. I'm used to use sem package. I'm not familiar with
> > lm(). I trid summary(lm(B ~ A*C)) and failed to get any result.
> >
> > Can sem deal with mediation? And could you tell me the command of
> > generating a interaction item of A (nxp) and C (mxp)?
> I don't use sem, but I don't see why you need it for this.  This
> is a simple regression problem, so far as I can tell.
> I think you need to do some reading of the R documentation.  What
> are A, B, and C?  They should be vectors.  That was the point of
> my comment about rowMeans.
> You seem to be guessing and relying on authority instead of
> trying to understand.
> --
> Jonathan Baron, Professor of Psychology, University of Pennsylvania
> Home page: http://www.sas.upenn.edu/~baron

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