> Date: Mon, 23 Jul 2012 15:36:19 -0400
> From:
[log in to unmask]> Subject: Re: [FSL] GLM - ANOVA with covariates
> To:
[log in to unmask]>
> The designs are different and have different assumptions about the
> data. The following website has a great explanation of your two
> models:
>
> http://mumford.fmripower.org/mean_centering/
>
> Best Regards, Donald McLaren
> =================
> D.G. McLaren, Ph.D.
> Research Fellow, Department of Neurology, Massachusetts General Hospital and
> Harvard Medical School
> Postdoctoral Research Fellow, GRECC, Bedford VA
> Website: http://www.martinos.org/~mclaren
> Office: (773) 406-2464
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>
> On Mon, Jul 23, 2012 at 5:52 AM, Giulia Preti <
[log in to unmask]> wrote:
> > Hi there,
> >
> > I'm running an fMRI analysis and I'm trying to set up a design matrix to perform an ANOVA with 3 groups of subjects (controls, two groups of patients) and one covariate (task performance).
> >
> > I set up the design matrix like in the example below:
> >
> >
> > Group EV1 EV2 EV3 EV4
> > 1 1 0 0 9,70
> > 1 1 0 0 9,70
> > 1 1 0 0 9,70
> > 1 1 0 0 9,70
> > 1 0 1 0 7,70
> > 1 0 1 0 4,14
> > 1 0 1 0 -12,52
> > 1 0 0 1 -10,30
> > 1 0 0 1 -20,86
> > 1 0 0 1 -6,97
> >
> > CONTRASTS:
> >
> > 1 -1 0 0
> > 1 0 -1 0
> > 0 1 -1 0
> > -1 1 0 0
> > -1 0 1 0
> > 0 -1 1 0
> >
> >
> >
> >
> > Is this correct? Is it the same if I specify the value 1,2,3 for the column "Group" and split the performance column (EV4) in 2 different columns like below (demeaning for each column separately and deleting the column of the controls'performances, since it woul be all 0)?
> >
> >
> > Group EV1 EV2 EV3 EV4 EV5
> > 1 1 0 0 0 0
> > 1 1 0 0 0 0
> > 1 1 0 0 0 0
> > 1 1 0 0 0 0
> > 2 0 1 0 7,3 0
> > 2 0 1 0 3,75 0
> > 2 0 1 0 -12,9 0
> > 3 0 0 1 0 2.41
> > 3 0 0 1 0 -8.15
> > 3 0 0 1 0 5.74
> >
> >
> >
> > What is the difference between the two designs, and which is better?
> >
> >
> > Thank you in advance for your help.
> >
> >
> > Giulia