Hello SPM world,

I have a few questions about how to perform the group analysis in SPM12.

My questions are the following:

1. How to confirm that the group mean volume created by SPM is sensible and accurate?

              One of my subjects appears to be tilted, meaning that the A-P line is not centered in the middle of the image, like the rest of my subjects. I'm guessing I have to fix this subject before moving forward but I'm not sure how.

        *data was preprocessed using fmriprep, which uses FreeSurfer for most of

         the anatomical processing.1st-level analysis was also successfully done for all subjects.

2. How do I create the contrast design matrix containing all runs for all subjects?

              I understand I need to use the beta nifty files of interest of all subject in order to perform a 2nd-level analysis, but I don't know how to specify my model with the conditions of my experimental paradigm: 3 feature classes (ex.color), each feature class has 6 possible values (ex.magenta,teal,orange,...).

Any help is much appreciated.

Thank you,