Dear SPM community,
I’ve been looking around for a “decent” way to run a 2-way mixed ANOVA on my fMRI data (acquired within a mixed experimental design), but I’m not quite sure I’ve managed to grasped all the subtleties in SPM (… getting a little confused with all the information I’ve read on this topic). Therefore, I was hoping someone could let me know if I’m doing the right thing with regards to the following:
I have 2 groups (group1, group2) and 3 within-subjects conditions (task 1, task 2, reference task).
In order to assess the main effects of groups, tasks of interests (1 & 2) and a potential interaction, I’ve used the “full-factorial” option of SPM8 within a 2x3 within-between subjects model (Groups: independence = yes, variance = unequal; Conditions: independence = no, variance = equal).
Since I’m also interested in running post-hoc t-test contrast between various conditions (ex.: “task1 vs reference task”, “task 1 vs task 2”), I’ve chosen to use my “reference task” at the 2nd level instead of contrasting it to my tasks of interests (1 & 2) at the 1st level (otherwise, a 2nd level “task1 vs ref” vs “task2 vs ref” contrast is getting a bit “restrictive” and no significant activation/deactivation shows up).
Thus, considering that I’m interested in main/interaction effects and post-hoc contrasts, is it right for me to use a 2x3 “full-factorial” design? Perhaps a flexible factorial with the “subjects” condition would be more appropriate to “control” for non-contrasted conditions?. Moreover, is it appropriate to include a reference task at the 2nd level, since I don’t plan of using it on all my post-hoc contrasts ?
Any help/comment would greatly appreciated,
Yannick
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