If there is no interaction between F/R and Active, then there should not be any
theoretical difference between the two analyses, except that FR combined will
be slightly more powerful since it has one more degree of freedom. You should
first use the uncombined model to look for an interaction, and then proceed
with the combined if there is no significant interaction.
There are several other things that could also come into play. First, it looks
like the Rs have a much higher active score than Fs. This will create some
correlation in the uncombined model and weaken the power. Second, it looks like
there might be more Sex=1 in the R group; this will also weaken the uncombined
model.
One more thing: you are not modeling sex properly. You should create four
Classes (F-Male, F-Female, R-Male, and R-Female)
On 8/19/2019 8:32 AM, tange_neuro wrote:
External Email - Use Caution
Hi all,
I am deeply confused and terribly needed some help, and I failed to find the
answer in the Freesurfer website.
I had two patient groups F and R. To analysis the correlation between active
time and cortical thickness, I tried two different methods A and B (A, treating
patients in different group F and R as shown in attached figure A; B, treating
all patients as one group FR as shown in attached figure B), and got distinctly
different results.
So, my questions:
1、Which one is actually correct for calculating the correlation between active
time and thickness, and what does the other one mean?
2、Does "--cache 3 abs --cwp 0.999" means that the result is only corrected with
vertex level P < 0.001, and no cluster level correction is conducted?
I am looking forward to getting your help.
Sincerely yours,
Ge Tan
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