 |
 |
Dear all I have looked through the SPM archive and I see that conjunctions at the second level are a recurrent topic. Despite looking through old archives I am still not exactly sure how to carry out a conjunction at the second level in SPM8 with my data. My experiment is as follows. I have one group of 12 subjects and 4 conditions: A, B, C, D. I am interested in the conjunction of AC > BD and AB > CD. At a single subject level I have carried out the conjunctions. I have con images for t-tests at the first level, ie A>C, B>D; A>C, B>D, and now want to carry out the conjunctions of those at the group level. I am thinking that I could create two seperate, two sample t test designs corresponding to each of my conjunctions (AC > BD and AB > CD) using the con images of the individual ttests as group factors. For example to explore AC > BD, I would use the ttest con images for all subjects for A>B as one group factor and C>D for the other. Then using the control button I can create conjunctions in the contrast manager. I would then do the same for the other conjunction AB > CD, using A>C and B>D. When I do this I get a very sensible looking SPMs... I would be grateful for any advice. Thank you in advance, Sam