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Angela,

The conjunction means that A and B (and C) are both(/all) significant. Then you will want to threshold each so that they are individually significant. Then you can look for areas that overlap between conditions.

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 Wed, Oct 2, 2013 at 7:23 PM, Angela J <[log in to unmask]> wrote:
Dear SPMers,

I'm confused about the relationship between thresholding a conjunction and the individual contrasts that will enter the conjunction. Let's assume I want to use a p value of 0.001 (uncorrected) for the conjunction using two different constrasts. What threshold should I apply to my two individual contrasts? And what if I have three separate contrasts, etc? If the conjunction is thresholded at 0.05 (corrected), what threshold should my individual contrasts have then?

Thanks in advance,

Angela