Dear FSL experts
I'm looking for some advice with a question I met using randomise for TBSS. I have 3 groups and I wants to find out differences in white matter between them with 2 covariates of no interest (age and education). I ran an F-test using randomise with the following F-test contrasts
design.mat
/NumWaves 3
/NumPoints 101
/PPheights 1 1 1
/matrix
1 0 0 40 14
1 0 0 58 12
1 0 0 40 12
.
.
.
0 1 0 33 12
0 1 0 35 12
.
.
.
0 0 1 59 14
0 0 1 53 9
design.con
/ContrastName1 CON
/ContrastName2 NHE
/ContrastName3 MHE
/NumWaves 3
/NumContrasts 3
/PPheights 1 1 1
/RequiredEffect 0.638 0.629 0.689
/Matrix
1 -1 0 0 0
1 0 -1 0 0
0 1 -1 0 0
design.fts
/NumWaves 3
/NumContrasts 1
/Matrix
1 1 1
I used the following command to run the F-test
randomise -i all_FA_skeletionised -o tbss -m mean_FA_skeleton_mask -d design.mat -t design.con -f design.fts -n 5000 -x --T2
when doing 3rd contrast (tbss_vox_corrp_tstat3), it appears the following message:
The unpermuted statistic image for the current image contains no positive values, and cannot be processed with TFCE. A blank output image will be created.
Is there something wrong with my contrast since when I did the statistics with SPM, there were some positive results coming up.
I would really appreciate any advice. Thanks!
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