Hello Team AFNI,

I am trying to run a multilevel model using 3dLME. I have two factors in the model, Group (2 levels) and Age (continuous; random effect). Initially, I coded Group as 1 and 0, so that the intercept is when Group=0 (see script A below). Then, I recoded Group as 0.5 and -0.5 (script B below), so that the intercept would be halfway between the two groups. However, this produced the exact same results as when Group was coded as 1 and 0. When I pull ROIstats and run the model separately in R, I get different results depending on how I coded Group.

So my questions are:

How does 3dLME treat the Group variable? And what does it feed into R?
Am I coding it correctly?

Script A

3dLME -prefix lme-B+C \
-jobs 4 \
-model 'Group*Age' \
-qVars 'Age' \
-qVarCenters '14.79' \
-ranEff '~1|Subj' \
-resid lme-B+C-resid \
-dataTable \
Subj Group Age InputFile \
A1 1 15.37 'input+tlrc[18]' \
A1 1 17.45 'input+tlrc[18]' \
...
...
A45 0 13.68 'input+tlrc[18]'
A45 0 16.01 'input+tlrc[18]'

Script B

3dLME -prefix lme-B+C \
-jobs 4 \
-model 'Group*Age' \
-qVars 'Age' \
-qVarCenters '14.79' \
-ranEff '~1|Subj' \
-resid lme-B+C-resid \
-dataTable \
Subj Group Age InputFile \
A1 0.5 15.37 'input+tlrc[18]' \
A1 0.5 17.45 'input+tlrc[18]' \
...
...
A45 -0.5 13.68 'input+tlrc[18]'
A45 -0.5 16.01 'input+tlrc[18]'

Thank you!
Jordan



Edited 1 time(s). Last edit at 01/04/2017 03:53PM by Jordan.