Hello Experts,
I have a question about design matrix for two-sample T-est with a covariate.
Let say I have two groups of subjects (eg 3 patients and 4 controls - actual
numbers are larger) and response time as a covariate. Two-sample T-test is
very clear because an example is explained in a FSL document. I am not sure
how to include response time to find out the effect of it.
Let ev1=patient, ev2=control, ev3=all, ev4= demeaned response time
group ev1 ev2 ev3 ev4
1 1 0 1 24
1 1 0 1 -18
1 1 0 1 -7
2 0 1 1 5
2 0 1 1 -4
2 0 1 1 6
2 0 1 1 6
For contrasts,
Patient-Control : 1 -1 0 0
Control-Patient : -1 1 0 0
Response time: 0 0 0 1
Are these correct?
I am not sure if I should include ev3 and if I should set ev4 for each group to
find out response time effect for patients and controls, respectively.
Any help will be greatly appreciated.
Hyo Jong
|