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) j.haenggi@psychologie.uzh.ch (email) http://www.psychologie.uzh.ch/neuropsy/ (website) http://www.juergenhaenggi.ch (private website)
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