You will get different results if the models are different.
(1) Are all the columns in the design matrix the same?
(2) Are the dependence and variance settings the same?
Differences in either of these will lead to differences in the results.
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 Thu, May 2, 2013 at 3:09 PM, Kailyn Bradley <[log in to unmask]> wrote:
> Hello SPM Users,
>
> I recently did a paired t test at the second level to look at the
> differences between two within-suibject conditions. I also attempted to do a
> one way within-subjects anova to compare the conditions; however I get
> slightly different results. The differences aren't huge (there's not
> completely different patterns of activation), but the cluster sizes
> especially are a little different and one of the clusters present in the
> ttest is not present in the anova. I was under the impression that a paired
> ttest with two conditions and a within-subjects anova with two conditions
> should yield the same results.
>
> Can anyone articulate for me why there might be differences between the two?
>
> I searched the SPM archives and it seems that when using the flexible
> factorial design for a within-subjects anova, some people get slightly
> different results than if they did a paired ttest. Does anyone know why?
>
> Thank you,
> Kailyn
>
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