I am trying to replicate some event-related analysis in FSL that I did
with UCLA's AIR tools and I am getting an error that my design is rank
deficient.
Here is the setup:
I have seven types of questions A,C,L,M,R,T,U. The TR is 4 and I
collected three volumes for each question (the question, the answer,
and the rest: q, a, r).
In the AIR tools, I specified three contrasts of C vs L & M, L vs. C &
M, and M vs C & L. I included all three volumes (qar) in the contrast
design as follows:
C vs L&M:
q a r
C -1 -1 8
L -1 -1 -1
M -1 -1 -1
L vs C&M
q a r
C -1 -1 -1
L -1 -1 8
M -1 -1 -1
M vs C&L
q a r
C -1 -1 -1
L -1 -1 -1
M -1 -1 8
The results fit substantive expectations beautifully. But, I want to
take advantage of FSL's mixed effects abilities.
So, I specified nine EVs corresponding to Cq, Ca, Cr, Lq, La, Lr, Mq,
Ma, Mr. And, I tried to set up the contrasts like I had in the AIR
tools.
C vs LM -1 -1 8 -1 -1 -1 -1 -1 -1
L vs CM -1 -1 -1 -1 -1 8 -1 -1 -1
M vs CL -1 -1 -1 -1 -1 -1 -1 -1 8
What am I doing wrong? How do I replicate the AIR results in FSL?
I have verified that the custom 3 column files specifying the timing of
the EVs is correct.
Of course, I know that EV1, EV2, and EV3 are not independent, but I am
not sure how to replicate the AIR results without setting up the same
contrast.
By the time I get to the course in Marina del Rey, I will have a very
good understanding of FSL, I think. But, since I have to have my data
analysis done for a deadline before the class, I appreciate your
indulgence with the ceaseless barrage of questions.
Darren
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