Dear AFNI experts,
I’m comparing different resting state measures between 3 patient groups and controls. I have to covariate a parameter of the movement of the subjects in the ANOVA I performed between my groups of subjects (4 groups) and in the t-tests comparing these groups (I used 3dANOVA before). The code I used is below. I have the following questions:
- is 3dMVM the right choice?
- is the syntax in gltcode and glfcode correct for my purpose?
- if I look at the results of the MVM on the brick showing only the effect F of “Group” variable I don’t get exactly the same results as the ANOVA without the covariate I had done before using 3dANOVA (they’re similar, clusters are significantly smaller in 3dMVM); are they supposed to be different?
- I read the guide about multiple centers for quantitative variables and concluded that it might be better to choose multiple centers (the mean Movement in the groups) to account for the possible interaction between group and movement, even if the interaction between group and movement is not significant tested in an ANOVA. I also tried to use a single center for the Movement variable (I did not put the qvarcenters option) and I got exactly the same results as for multiple centers. Might this be because the groups don’t differ enough in Movement? Should the centers in the qvarcenters options be written in a specific order?
- In my case, is it the same to put the quantitative variable Movement inside glfcode and gltcode or not? I got exactly the same results trying both alternatives.
The results I obtained are a bit problematic and I’d like to be confident that I ran the analyses correctly.
3dMVM -prefix MVM_GROUP_MOVEMENT -jobs 8 \ -bsVars "Group*Movement" \ -qVars "Movement" \ -qVarCenters '(0.0450,0.0607,0.0575,0.0492)' \ -mask './groupmask/cortex_be+tlrc' \ -num_glf 1 \ -glfLabel 1 Group -glfCode 1 'Group : 1*A & 1*B & 1*C & 1*D Movement :' \ -num_glt 6 \ -gltLabel 1 A-C -gltCode 1 'Group : 1*A -1*C Movement :' \ -gltLabel 2 B-C -gltCode 2 'Group : 1*B -1*C Movement :' \ -gltLabel 3 D-C -gltCode 3 'Group : 1*D -1*C Movement :' \ -gltLabel 4 A-B -gltCode 4 'Group : 1*A -1*B Movement :' \ -gltLabel 5 A-D -gltCode 5 'Group : 1*A -1*D Movement :' \ -gltLabel 6 B-D -gltCode 6 'Group : 1*B -1*D Movement :' \ -dataTable \ Subj Group Movement InputFile \ Subj001 D 0.0712 ./subj001/DC/DC_Z+tlrc \ ...