Hello,
I am doing my master's thesis on a longitudinal DTI-study about children with high risk for developmental dyslexia and I am not sure if I set up my design matrix, contrast file and exchangeability-information correctly. I am interested in whether poor readers developed differently than good readers over time. I have 2 timepoints, I want to compare. So, I think I need to look at the interaction of time and reading group. (Correct?)
The files for creating the TBSS skeleton and mean-FA image are in the following order:
subj1_scan1
subj1_scan2
subj2_scan1
subj2_scan2
...
subjN_scan1
subjN_scan2
I created text-files for design-matrix, contrast and exchange-info, to convert them with Text2Vest later on.
My design matrix looks like this:
1. column (time-effect): 1 for scan 1, -1 for scan 2
2. column (reading group): -1 for poor readers, 1 for good readers
3. column (interaction effect): value from 1. column multiplied with value from 2. column for interaction of time and reading group
4.-n. column (subject effects): 1 if it is the same subject, rest 0
(N+1). column: age because I want to control for that
(N+2). column: gender because I also want to contral for that (-1=f, 1=m)
So for example, it would look like this:
1 -1 -1 1 0 0 ... 7.20 1
-1 -1 1 1 0 0 ... 7.48 1
1 -1 -1 0 1 0 ... 7.06 -1
-1 -1 1 0 1 0 ... 8.71 -1
... ... ... ... ... ... ... .... ...
1 -1 -1 0 0 ... 1 7.65 -1
-1 -1 1 0 0 ... 1 8.65 -1
My contrast file would be: 0 0 1 0 ... 0
0 0 -1 0 ... 0
And my exchange-matrix:
1
1
2
2
...
...
n
n
Did I set up these files correctly?
Would be great if anybody could verify or correct. Thanks in advance.
Franziska
########################################################################
To unsubscribe from the FSL list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=FSL&A=1
|