I will be very grateful for your help on this. I use spm 2. I have just completed a pet study with 8 subjects scanned in 4 conditions with 3 scans each ( total 12 scans) - baseline and 3 other conditions. when I am comparing one of the 3 conditions vs baseline, should I put in all 12 scans for 4 conditions for each subject as in ... 1 1 1 2 2 2 3 3 3 4 4 4 ? then for e.g to compare condition 2 > condition 1, put the contrast as [ -1 1 ] ?
Or alternatively, just put the scans of interest only for a particular comparison.. so for the above e.g... 1 1 1 2 2 2 in conditions and then [-1 1] in contrast ?
which is the more scientific method? the degrees of freedom would be different in the 2 situations.
I will be very grateful if anybody could help me with this..
thanks in advance.
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