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Dear SPMers, I have made an experiment where 20 people had to look at fearfull images vs neutral images. Each subject watched the same run 4 times, with 1 parameter varying each time (so in total I have 4 times for the same run). But I can’t compare the 4 sessions together because they differs from the previous one by a single parameter. For instance the 3rd session differs from the 1st one by 2 parameters. To see if one parameter has an effect, I have done a paired t-test between 2 conditions (time 1 vs time 2 ; time2 vs time 3 ; time 1 vs time 4). First I would like to know if the paired t-test is appropriate and second, I am not sure which contrast (F or T) I am supposed to use. Is it correct to do a F test with the vector [-1 1] (cf. picture attached to this mail) or do I have to complete for all the columns [-1 1 -1 1 -1 1...] ? Any help would be more than appreciated! Thank you very much in advance. Julie