I ran into troubles with a 2x3x3-Within-Subject-Design. The idea is one group with 14 subjects, three factors, overall this makes a 2x3x3-Design (I ran models on single-subject level and now would like to conduct a group analysis based on the con images. Due to the Design, I have 18 con images per subject, each con images corresponding to one stimulus combination and contrasted against implicit baseline).
I'm interested in any of the potential main effects as well as the three possible two-way interactions and the three-way interaction.
"Flexible factorial" does not allow for any three-way interactions, so this option seems to be useless. The extension GLM_flex http://nmr.mgh.harvard.edu/harvardagingbrain/People/AaronSchultz/GLM_Flex.html does not provide any solution for my design as well.
Thus it seems to me that I have to run a "Full Factorial" as it is the only design in which I can look at three-way interactions at all. So I set up a model with three factors with "Independence - No" and "Variance - Equal". But as far as I understood based on other messages dealing with 2x2 or 2x3 ANOVAs, this is statistically wrong for a within-subject design?
Would it help to add another factor "Subject"? If not, any other ideas?
Your help is greatly appreciated!