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Dear all, I have a question regarding the analyses of PET data with SPM. We have 25 subjects in three groups and they were measured during 3 distinct conditions. Besides, these conditions consisted of up to three repetitions. Now we would like to test for significant differences in the activation between the three groups but also for differences within the groups with SPM. So we have a 3x3 repeated measures ANOVA. As I am not very experienced with GLM in SPM I have been searching this forum. Yet, i have some remaining questions. First, what are the advantages of using GLMFlex? There have been several threads about this but I didn't really understood the point about it. And second, using a flexible factorial design (if possible), is there any tutorial or explanation for the contrasts to be used? Applying the one of gläscher et al. was helpful. For this we defined three factors (subject, group, condition). However,we are not sure how to define contrasts to detect interactions. We are looking for a help to understand what we have to do to answer our hypotheses and would be grateful for any kind of help like links to e.g. comprehensive tutorials or something. Thanks in advance David