Dear FSLers
I intend to do unpaired two-sample t-test with IQ scores as confound
regressor. I designed events and contrasts like this:
------------------------------------------------
EVs
Number of main EVs 3
Number of addition, voxel-dependent EVs 0
Group EV1(group_A) EV2(group_B) EV3(demeaned_IQ)
1 1 0 -9.7
1 1 0 1.2
: : : :
2 0 1 12.2
2 0 1 -10.0
Contrasts
Contrast 2 F-tests 0
for_group_A>group_B 1 -1 0
for_group_B>group_A -1 1 0
When I saved the design, there was a warning window jumped out with the
following message:
Problem with processing the model: Warning ¨C design matrix uses different
group (for different variances), but these do not contain ¡°separable¡± EVs for
the different groups ( it is necessary, that, for each EV, only one of the
groups has non-zero values).
My questions are,
1) Shall I treat all subjects as group ¡°1¡±, or shall I split IQ scores as two
events? If I split IQ scores as two events, shall I demean IQ scores
separately in each group or across all subjects?
2) In randomise command, I needn¡¯t use option ¨CD since I have demeaned
IQ scores, am I right? There is a file named design.grp produced by Glm_UI,
is ¨Ce option necessary in randomise?
Must I use ¨Cx option in randomise? May I use --T2?
Thanks a lot.
sincerely, Yuzheng
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Biox-lab, Zhejiang Univ. China
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