Hi all,
I was adviced to use PALM for permutation of non-orthogonal surface data. However, I have some questions regarding the design matrix en contrast files to be used in PALM, but somehow I cannot subscribe to the FSL mailing list, and I was hoping one of the freesurfer users could help me out.
I have a complex design and I would like to test for interactions as well for subgroups; in addition, I have several covariates. If I use the following collumns:
A1 B1 A2 B2 cov1 cov2 cov3 I assumed I can at least test for the effects of A vs B (1 - 1 1 -1 0 0 0) and 1 vs 2 (1 1 -1 -1 0 0 0) and interactions (1 -1 -1 1 0 0 0).
Q1: Is it true that I cannot compare subgroups, because columns denoted zero will be handeled as being a covariate? i.e. the contrast 1 -1 0 0 0 0 0 is inappropriate and I would have to build a new design matrix (A1 B1 cov1 cov2 cov3)? This is what I was told previously when using randomise for DTI data, but I'm not sure PALM works the same way.
Q2: What I also understood from randomise is that you have to define both 1 -1 and -1 1; there is no option for a 2tailed t-test or F test. Is that correct and does it also apply to PALM?
Thanks,
Maaike