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Dear Donald,
Thanks a lot. I have also another question regarding the number of subjects! I have about 15 subjects in each group, and I was wondering if I should go for non parametric methods for the statistics?
Should I go for the Snpm toolbox or there would be some alternatives to that? How should one decide on using the parametric or non-parametric statistics in this case?
Thanks a lot in advance!
Shahrzad
From: "MCLAREN, Donald" <[log in to unmask]>
To: [log in to unmask]
Sent: Thursday, May 31, 2012 4:46 AM
Subject: Re: [SPM] Flexible Factorial model

You could either use a 2x2 and then test each against the controls OR you could use a 1x5 ANOVA as you have 5 groups.

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and
Harvard Medical School
Website: http://www.martinos.org/~mclaren
Office: (773) 406-2464
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On Wed, May 30, 2012 at 11:48 AM, shahrzad kharabian <[log in to unmask]> wrote:
Dear SPMers,
In a VBM study of patients I have a complete 2x2 Design (2 Factors : health situation at the moment and therapy (if they have gone under therapy or not)) each of the factors having 2 levels (sick/healthy, with therapy/without therapy).  I have also a control group which is not at all affected by the virus(so is healthy and has gone under no therapy!). I am wondering what kind of a design matrix would give me the possibility to do the comparisons between the control group and each of other groups in the same design as I could look at the main effects of therapy and heath situation or the interactions!

Is it the Flexible Factorial model(2 x 2 x 2)? Is it recommended to pull all groups in to one model or it would be better to apply a full-factorial model 2x2 for the patients and then separately do t-tests with the control group?
 
Thanks a lot for your "Detailed" helps in advance!

Shahrzad