Hello all,
I am having a problem figuring out how to detect and remove outliers from my
data set in spm2. I have a PET study with 3 treatment groups of 17, 17, and
20 subjects each, all having a pre- and post- treatment scan. I believe
this group is large enough to remove outliers, however I have not been able
to do so.
I used spmd to examine my data, and it provided an image with number of
outliers per voxel. However, that is not what I am looking for, nor does it
indicate which ones are the outliers (as far as I know). I would like to
remove subjects based on the difference from pre- to post- treatment.
The only method I have thought to do this would be use imcalc, create a set
of difference images (pre-post), and look at the mean value per image and
exclude based on that criteria. However, I am not sure if this is valid,
nor do I know how to actually do it.
Any advice on how to detect the outliers would be appreciated.
Thank you,
Matt Costello
|