Greetings TBSS and Randomize Experts,
I am still struggling to understand how to use Randomize to analyze my FA
data. Here are some basic questions and some more advanced ones:
1. I originally had a 2x3 design, but have decided to make life easier and
start with a 2x2 ANOVA design. The first factor is Time 1 and Time 2 (this
is a longitudinal study examining the impact of abstinence on white matter)
which I assume is a fixed effect, while second factor is Abstinent versus
controls which I assume is random effect. I had originally included a third
group of people who relapsed (so it was a 2x3), but to simplify things...I
will just go for 2x2. Since my all_FA_skeletonised.nii.gz already has the
cases, can I simply put zeros for the cases I want to take out and run
randomize, or do I have to go back and redo the prior steps to get a new
all_FA_skeletonised.nii.gz without the relapsers.
2. The design.mat I created has the following:
EV1(control time1)/EV2(control time2)/EV3 (abstinent time1)/EV4 (abstinent
time2)/EV5(subject1)/EV6(sub2)/EV7(sub3)...and so on with subjects.
I have tried several simple contrasts, but have not yet figured out how to
do the analysis the way a traditional 2x2 is done with simple behavioral
data. For example, how do I do an omnibus F-test (Omnibus ANOVA) to examine
if there is an interaction effect. What are the actual contrasts that need
to be included, and how do I indicate in Glm that I would like an omnibus
F-test ANOVA.
3. When an F-test is set up, how are the results displayed. Is there an
output file with specific regions in which these is a significant
interaction effect between the factors?
4. In order to run randomize F-test, is it necessary to have equal number of
subjects in each cell.
5. If there is an interaction, what is the next step, and if there is no
interaction what is the next step?
Thank you for your help.
Omar
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