I'd personally do a two-sample t-test to compare two groups of subjects.
You can use either the extracted values or the % signal change.
Z-scores should not be used to compares groups for task data because
they reflect both the amplitude and standard deviation of the single
subjects. You could have a high Z-score in one group and a higher
amplitude in the other group, which would lead to confusion.
Furthermore, the interpretation is that group A as higher activity
than group B, which isn't explicitly true with Z-scores.
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
Office: (773) 406-2464
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On Wed, May 4, 2011 at 4:33 AM, Ben Becker <[log in to unmask]> wrote:
> Dear SPMers,
>
> a question regarding the further statistical analysis of extracted beta-values:
>
> My analysis:
>
> 1. I defined the task related network (2 groups of subjects, 3 memory load conditions; the contrast 1/3 load 1 + 1/3 load 2 + 1/3 load 3 vs
> implicit baseline was put forward in a one sample t-test)
>
> 2. I extracted individual beta values from clusters showing sign. activity in 1 (using marsbar)
>
> The aim of the present study is to compare the two groups of subjects. Now, is it valid to perform further statistical analysis on the extracted beta values? Or should z-values or %-signal change be used?
>
> Thanks in advance,
>
> ben
>
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