[Freesurfer] mri_glmfit long_stats_slopes with group

Dear Freesurfer,

I would like to test if the percentage change (two time points) of cortical thickness is different between two groups.

What i have done:

FIRST: long_stats_slopes --qdec ./qdec/long.qdec.table.dat --stats lh.aparc.stats --meas thickness --sd $SUBJECTS_DIR --do-spc --generic-time --stack-spc ./qdec/long.lh.aparc.stats.stack.txt

SECOND: mri_glmfit --osgm --glmdir lh_thickness.aparc-spc --table long.lh.aparc_thickness.stats.stack.txt

THIRD: cat lh_thickness.aparc-spc/sig.table.dat

Qesteions: 1. How do i test if there is a significant difference between the two groups? 2. How do i visualise this difference in FreeView?

Best regards Kasper Jessen