Dear FSLers,
I am new to FSL and am currently analysing 4 groups DTI TBSS data and have worked my way through the tutorial and posts on the mailing list. However, I am still confused with the F-Test.
If I include the -f design.fts option but not specify an -F [number] option, I get an error message that no specific option was selected but if I do say -F 1 then I get another error message. So concretely, I had used the example on the TBSS stats webpage:
randomise -i all_FA_skeletonised -o tbss -m mean_FA_skeleton_mask -d model_test1.mat -t model_test1.con -f model_test1.fts -n 5000 -c 2 -V
Message:
Loading Data:
Data loaded
1.16979e+44 permutations required for exhaustive test of f-test 1
Doing 5000 random permutations
Warning! No output options selected. Outputing raw tstat only
I had then tried
randomise options: -i all_FA_skeletonised -o tbss -m mean_FA_skeleton_mask -d model_test1.mat -t model_test1.con -f model_test1.fts -n 5000 -c 2 -f 1 -V
but got
Loading Data: ERROR: Program failed
An exception has been thrown
Unable to open 1
Exiting
_______
If my design matrix is such that
F-TEST
1 -1 0 0 check
1 0 -1 0 check
1 0 0 -1 check
……
…… set of remaining t-contrasts here without selection of F, e.g.,
0 0 1 -1 not checked
… etc
What option should I use in randomize to get the output for my F-test? Should I use a combination of these to specify the contrast or can I ignore the error and check this once the statistics have run?
Many thanks in advance for any suggestions!
Sven
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