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Dear SPM group, I just started to do random contrast. Here is my design: 12 subjects, four conditions (A B C D). I'd like to find out whether D is significantly greater than C in a random effect analysis. I did the following: (1) For each subject, get a Con***.img and Con***.hdr for the contrast of my interest (D-C). (2) In SPM99, choose "Basic Models" > "one-sample t-test", and enterred each subject's Con***.img as the images. The computation created an output "SPM.mat". My question comes in the next step. The SPM program asks me to use "Results" to assess results. So I clicked "Results", selected "SPM.mat" that I just created. But then the program requires me to specify a contrast. I am completely at a loss as what the "contrast" means. I tried some numbers, and it seems to ask me to input one number (e.g., 1) rather than a true contrast (e.g., 0 0 1 -1, with the sum = 0). Could you please explain what "contrast" means in this step? Your help is greatly appreciated. Thank you. Yuhong