Dear FreeSurfer experts,
Hello, I started to use FreeSurfer recently.
I want to do group analysis with QDEC in order to compare 2 groups
(control group and patient group), regressing out age and gender.
When I include 2 discrete factors (diagnosis and gender) and 1
continuous factor (age), and run QDEC,
there appear a question of "Does the average thickness, accounting for
Gender, differ between Controls and Patients?",
but there NOT appear a question of "Does the average thickness,
accounting for Gender *AND AGE*, differ between Controls and
Patients?".
So, it seems that age cannot be regressed out in this way.
However, when I include 1 discrete factor (gender only) and 2
continuous factors (age and
also diagnosis *dummy parameterized: Controls = 1, Patients = 0*), and run QDEC,
there appear a question of "Does the correlation between thickness and
Diagnois, accounting for Age and Gender, differ from zero?",
and the result seems OK.
My question is;
1) Is it right to do the (above-mentioned) latter way to compare
difference of thickness between the 2 groups, regressing out age and
gender?
2) Why couldn't age regressed out in the former way?
3) In this way, generally is it OK if I enter simple "discrete" factor
as a continuous factor in QDEC (for example, gender:male=1, female=0)?
This time I want to ask, since I couldn't find an answer in the past archives.
Thanks a lot,
Manabu Kubota
kubotajp(a)kuhp.kyoto-u.ac.jp
Graduate School of Medicine, Kyoto University