Dear SPM'er,
I have a question concerning the use of "mask with other contrasts" in the
second level analysis.
I have two differnet conditions A and B and a baseline (C) condition.
I would like to use the baseline contrast (A minus C) as an implicit
positive mask for the differential contrast (A minus B).
After selecting the mask contrast, I have to determine the uncorrected
p-value of the mask.
Having tried out different p-values for the mask, I found out that they
automatically change the p-values of the masked differential contrast.
How are the significance thresholds of the mask and the masked differential
contrast related? Does the use of a mask improve the error rate?
I hope someone can help me with this question.
Best regards,
Ruth
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Ruth Schubert
Berlin NeuroImaging Center
Charité Campus Mitte
Department of Neurology
Schumannstr. 20/21
10117 Berlin, Germany
Phone: ++49-30-450 560 195
Fax: ++49-30-450 560 952
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