Dear Joelle,
Well, there are different options. E.g. set up one contrast [1 -1 ...] on single-subject level to test for "first five" > "second five" and a second contrast [0.5 0.5 ...] corresponding to "average" = (first five + second five)/2.
To test for differences between first and second five trials on second level set up a two sample t-test based on the first con images (first bunch of files selected = group 1, second selection = group 2). Within this second level model, [0.5 0.5] corresponds to "first five" > "second five" across groups, [-0.5 -0.5] corresponds to "first five" < "second five" across groups, [1 -1] corresponds to "(group 1 first five - group 1 second five) > (group 2 first five - group 2 second five)", [-1 1] corresponds to "(group 1 first five - group 1 second five) < (group 2 first five - group 2 second five)"
To test for group differences across conditions set up a two-sample t-test based on the second con images, the corresponding contrast vector within the scond-level model is [1 -1] for group 1 > group 2 and [-1 1] for group 2 > group 1.
Hope this helps
Helmut
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