If you have two groups and a single covariate, when you run it with
mri_glmfit create a contrast with [0 0 1 -1]. In QDEC, it will be one of
the default contrasts (something like "do the two groups differ in slope?")
doug
On 1/12/14 5:31 AM, amirhossein manzouri wrote:
Thanks Doug and how can check if the slopes are different?
On Jan 12, 2014 12:33 AM, "Douglas Greve" <gr...@nmr.mgh.harvard.edu
<mailto:gr...@nmr.mgh.harvard.edu>> wrote:
Use DODS to test whether the slopes differ between the three
groups. If they do not, then use DOSS.
doug
On 1/11/14 5:03 PM, amirhossein manzouri wrote:
Thanks Doug for the prompt reply. I just want to if DODS is ok to
be used in my case or I should use DOSS?
On Jan 11, 2014 10:56 PM, "Douglas Greve"
<gr...@nmr.mgh.harvard.edu <mailto:gr...@nmr.mgh.harvard.edu>> wrote:
HiAmirhossein, don't use the DOSS feature in QDEC because there is a
bug such that
it does not always do the right thing. Sorry, I sent out an email
about 8mo ago on this, but it is not easy to let people know about a bug
once the bug is out there. If you want to use DOSS, use mri_glmfit
directly. If you still have a question,
then repost to the list.
doug
On 1/11/14 1:22 PM, amirhossein manzouri wrote:
Hello all,
I am using Qdec (version5.1) to study cortical thickness
differences between groups having Age as nuisance covariate.
I do not have assumption if the groups are different or not
. Using DODS and DOSS gives me completely different
results. We have three groups including 41, 39, and 24
subjects in each.
My question is which results design matrix type is more
reliable for such a study? And also what if I include a
covariate of interest in my comparison?
Thanks in advance,
Best regards,
Amirhossein Manzouri
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