As Marko states, option 1 should be used. Option 2 can provide you
completely the wrong interpretation based on the threshold chosen.
An extreme example, at time 1, the Z-score in all voxels is 2.999. At
time 2, the Z-scores in all voxels is 3.000. Subtracting the maps
would lead to the conclusion that there is no difference between time
1 and time 2. Comparing cluster sizes would lead to the conclusion
that there are huge differences.
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 Fri, Aug 2, 2013 at 10:07 AM, Paulo Marques
<[log in to unmask]> wrote:
> Thank you once again Marko,
>
> Your opinion is in line with what I thought. Unfortunately we won't be able to get more subjects but we have this data and we would like to analyze it somehow. I'm thinking about two alternative analysis without inferring about significance:
> (I) subtract the networks' Z-maps of different time-points and characterize the differences within the corresponding network mask;
> (II) apply the same significance threshold on the Z-maps of each time-point and interpret the differences in cluster size.
>
> Does this seem "ok" considering the circumstances?
>
> Best regards,
> Paulo
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