[R] Adjusted Means

John Fox
Mon, 17 Oct 2011 20:29:23 -0000

Dear Mattune,

I guess that you're using the effect() function in the effects package.
You've requested the effect for the covariate fixing the values of the
factors, rather than vice-versa. Try effect("a*b*c", Anocova.Model)
or, for
more detail in the output, summary(effect("a*b*c", Anocova.Model)). I
assume, BTW, that you fit the model X ~ a*b*c + d, with d the covariate,
rather than what you said you did.

I hope this helps,
 John

--------------------------------
John Fox
Senator William McMaster
  Professor of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
http://socserv.mcmaster.ca/jfox




> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
On
> Behalf Of Mattune
> Sent: October-17-11 3:45 PM
> To: r-help at r-project.org
> Subject: [R] Adjusted Means
>
> I'm running the following ANCOVA model in R: X=a*b*d + d where d is the
> covariate.  I want to produce adjusted means for X for all possible
treatment
> combinations.  a has 6 levels, b has 2 levels, c has 2 levels, so this is
a
> 6x2x2 = 24 possible treatment combinations.  When I run:
> effect("d", Ancova.Model) I am given only 20 adjusted means
(also, I'm not
> exactly sure of how the adjusted means are reported, that is, which one
> represents which treatment combination...what order are they in?)  Any
> ideas??
>
> Thanks!
> Master's Student in Maine
>
> --
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