dear John, spmers,
I had the following questions regarding the statistical
tests for a particular experiment i am doing now. My data consists of
certain texture features derived from MRI and segmentation maps, which are
combined in a single number at each voxel. I wanted to compare these
responses across a group of normal controls, and get a spm of where these
values significantly differ in the patient.
Currently i am using "1 scan/subject Ancova", with one
group containing the normals, the the second group containing a single
patient. The volumes are normalized and smoothed at 8mmFWHM.
My question to the group is, is this a correct analysis
for the comparison?
Further, i have observed the following. The way the
texture features are generated yields a sparse volume, and there are cases
where the values are zero/near zero at that voxel across all normals, and
substantially large in the patient. But these seem to get excluded from
the analysis. How does spm deal with those voxels where the response
variables are zero everywhere in the normals, but large in the patients?
And, how can i ensure that all the voxels within the brain get analysed?
I hope i have been able to put the question clearly.
thanking in advance,
Siddharth.
