The first one will test for a difference between group offset/intercept
accounting for age, gender, episodes, and residuals. By setting a
regressor contrast element to 0, one accounts for that variable because
the variable appears in the model that is fit to the data (and so its
effects already removed from other variables). One more thing: I would
recommend incorporating gender in the class structure not as a
continuous variable. So you would have 4 classes: PatentientsMale,
PatientsFemale, HCMale, HCFemale then use contrast [0.5 0.5 -0.5 -0.5 0
0 0 0 0 ...]
On 5/9/2024 3:26 PM, Liliana Wu wrote:
External Email - Use Caution
Hello!
I am having trouble with creating my contrast files. I did go over
FsfdExamples (*MailScanner has detected a possible fraud attempt from
"secure-web.cisco.com" claiming to be*
https://surfer.nmr.mgh.harvard.edu/fswiki/FsgdExamples
<https://secure-web.cisco.com/1ezcK_pFVwJfmWpdVsJeZORU_8kaDi3SfZnw3BO98zpMkJch-p_v87YwJzoqtiefk_hIobUKYja2omqZRjod-i1GdU-HkzipUmBlo5LVsklOHdteQtjAi1L5l1J_T5iRzcE-h_C2xiFxUcjQxPmDrQFVFDP-mFdgiDx4hibkUidw4NEsFW1XHiR7roksIT1GrgvmbILffvuecnvDO6Z8oTqSldk1jddeE0vQYO5WHK19PUmdcg_uW0gtN1EgAhq3AxmE2NcKh2djkfca5f3nqamoDBZ84nG1kz_J43CQgPHPe_lX5eVqUfcsPGuqiMUbpt15_ZNoCDBTS88hFbjyFVA/https%3A%2F%2Fsurfer.nmr.mgh.harvard.edu%2Ffswiki%2FFsgdExamples>).
However, I am unsure how should I create my contrast files if I want
do a 2 group comparison while controlling 4 covariates:
Class:
Patients, healthy control
variables are:
Age,gender,episodes,residuals,
Here is how I set up my contrast files:
1 -1 0 0 0 0 0 0 0 0 - Contrast1 (measure group differences)
1 -1 0.125 0.125 0.125 0.125 0.125 0.125 0.125 0.125 – Contrast 2
(measure group differences while accounting for covariates)
For some reason I think I am setting up those contrast files wrong…
Any help is appreciated.
Best,
Liliana
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