Dear Freesurfers,
Sorry if the question sounds too basic.
1. I am running an analysis on qdec with paired groups - normal and
patients,
To control for IntraCranialVolume(ICV),I am adding it as an 'nuisance
factor',Is it correct?
The suggested mode to add ICV to the tabled was to *demean* the ICV.
But when I subtract the mean values from individual subject ICV values,I
noticed that some of the subjects have a negative demeaned ICV value.
My question is - How should I proceed to include the data,ignore the
negative sign(because I thought a negative ICV makes no sense) and just
keep the values or retain the numbers with the sign.
Please correct me if I am going wrong in any of the steps.
However,I ran two analysis - one with the sign retained and other with sign
removed ,I noticed that both have very different results.
2. If I want to see the effect due to lithium within the patient group
(Between patients with and without psychosis) how should I design the
matrix in GUI.
I designed the following format
Fixed factor :- Diagnosis - Psychotic-pt
Non-Psychotic-pt
Co-variate :- Lithium use :- 1 - lithium user
0 - non user
Nuisance factor :- ICV
Is this design correct?
If not how should I construct it ?
Also what query would contain the result for anticipated question
My intention is to control for Diagnosis and then see effect/change due to
lithium use.
Thank you very much
--
Vikas B. R.
Medical student
Bangalore Medical College and Research Institute (BMCRI),
Bangalore,India,
Ph : +918904286825
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