Hi, sorry for the delay. In theory, DODS is better than DOSS because
you have an extra parameter you can use to fit the data and it will not
bias you to find a false positive. On the other hand, it does cost you
DOF, so if you have a small number of subjects, it can increase the
false negative rate.
Juergen Haenggi wrote:
Dear FS experts
We have done a group analysis with FS, but we are not absolutely sure which
is the most adequate design matrix to describe our data. We compared two
groups and used one covariate of no interest (mean thickness, total area,
etc.). Because there are two different options to create the design matrix
(dods and doss), we run the analysis twice, one time with dods and the other
time with doss, and unfortunately, we got two quite different patterns of
structural brain differences.
Is there any theoretical and/or empirical recommendation/clues in order to
decide which type of design matrix is more appropriate for our data?
Thanks in advance
Best regards
Juergen
-----------------------------------------------------------
Juergen Haenggi
Ph.D. (Dr. des.)
Division of Neuropsychology
Institute of Psychology
University of Zurich
Binzmuehlestrasse 14, PO Box 25
8050 Zurich, Switzerland
0041 44 635 73 97 (phone office)
0041 76 445 86 84 (phone mobile)
0041 44 635 74 09 (fax office)
BIN 4.D.04 (office room number)
[EMAIL PROTECTED] (email)
http://www.psychologie.uzh.ch/neuropsy/ (website)
http://www.juergenhaenggi.ch (private website)
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