Hi everyone,
I have a question related to setting up a 2x5 repeated-measured ANOVA model in FSL (2 groups x 5 factors), and testing the main effect of group across all levels. I have done my best to understand the design examples on the FSL GLM Wiki page (http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/GLM#Experimental_Designs_-_Repeated_measures).
In particular, my data have 5 experimental conditions per each subject, and I want to test for an effect of group across all the 5 conditions pooled together. If I understand the Wiki correctly (looking under ANOVA: 2-groups, 2-levels per subject (2-way mixed effect ANOVA)), the only way to test for group differences in this case is to do a within-subject average across all conditions/levels, and then run a 2 group mean comparison in a 3rd level analysis. I just want to confirm whether the approach I outline below is the correct way to go about this.
After setting up the GLM for each experimental condition with stimfiles in the first level analysis (within-subject), I then took an average across all five conditions (again, within-subject) as a second-level analysis. Next, in a third level analysis, I loaded the cope images of the "average" for each individual subject, indicating each subject's group with two EVs. I then performed a 2 group mean comparison on the second-level averages, which gave me results for the group main effect contrasts in both directions (1 -1 for control group - addict group, -1 1 for addict group - control group).
Is this approach the proper way to test for a main effect of group across all conditions under this setup (2x5 ANOVA with two groups and five repeated measures)? Any advice would be great. Please let me know if I have not described the analysis clearly enough.
Thank you very much!
John Sheppard
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