R help - Mar 2017 - Interpretation of lme results with intercorrelation between fixed factors

I?m running a mixed model analysis with 2 fixed factors that are intercorrelated
using the lme function and I?m having difficulties in interpreting the results.
As I?m quite novice I?ll try to use a very simple example.

My model is lme(Y~A*B). A has 3 levels (1, 2 and 3) and B has 2 levels (I and
II).
My results are something like this:



P statistic

B:II

P=0.01

A:2

P=0.01

A:3

P=0.09

II*2

P=0.61

II*3

P=0.031


My question is as follows. I understand that R keeps a level of each factor and
reports any statistical differences to it. So in this example it reports that II
is different than I and 2 against 3. However when it comes to the
intercorrelation, what does it report? Does it compare II*2 and II*3 to II*1 and
if so what happens with I*2 and I*3? Or does it compare II*2 to I*2 and II*3 to
I*3 and if so what happens to I*1 and II*1?

Thank you


Vasillis


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> On Mar 10, 2017, at 3:22 AM, Vasillis Papathanasiou <vpapathanasiou at
hotmail.com> wrote:
> 
> I?m running a mixed model analysis with 2 fixed factors that are
intercorrelated using the lme function and I?m having difficulties in
interpreting the results.
> As I?m quite novice I?ll try to use a very simple example.
I'm guessing this is perhaps the `lme` function in pkg:nlme. It's not
really an appropriate question for rhelp in any event. See the Posting Guide
(link below).
> 
> My model is lme(Y~A*B). A has 3 levels (1, 2 and 3) and B has 2 levels (I
and II).
> My results are something like this:
> 
Better to include actual output. I think most statisticians would advise
focussing on model comparisons rather than p-values of individual coefficients.

The experts hang out at:

https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models

... and they tend to be more welcoming for "interpretation" questions.

Or post to CrossValidated.com where this would be on topic. That group generally
tries to avoid purely R questions, but your question is so devoid of actual R
(no code and no actual output) that it would probably not be closed for that
reason.

Best;
David.
> 
> 
> P statistic
> 
> B:II
> 
> P=0.01
> 
> A:2
> 
> P=0.01
> 
> A:3
> 
> P=0.09
> 
> II*2
> 
> P=0.61
> 
> II*3
> 
> P=0.031
> 
> 
> My question is as follows. I understand that R keeps a level of each factor
and reports any statistical differences to it. So in this example it reports
that II is different than I and 2 against 3. However when it comes to the
intercorrelation, what does it report? Does it compare II*2 and II*3 to II*1 and
if so what happens with I*2 and I*3? Or does it compare II*2 to I*2 and II*3 to
I*3 and if so what happens to I*1 and II*1?
> 
> Thank you
> 
> 
> Vasillis
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
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David Winsemius
Alameda, CA, USA