The con*imgs are simply linear combinations (as determined
by the chosen contrast, provided it is estimable) of parameter
estimates (betas), NOT statistics (eg T values). Thus a voxel
value for a con*img created by contrast [1 0 0] would be simply
Beta1; the value for a con*img from [1 -1 0] would simply be
Beta1-Beta2.
Rik
Claire McGrath wrote:
> Dear SPMers;
>
> I was wondering how the contrast files were created. That is, what is the
> equation used to calculate the contrasts? Is is simple subtraction of T
> values?
>
> Thank you for your assistance with this matter.
>
> Claire McGrath
>
> --
> Claire McGrath, Ph.D.
> Neuropsychology Fellow
> Neuropsychiatry Section
> University of Pennsylvania
> 10th Floor, Gates Building
> Philadelphia, PA 19104-4283
>
> 215-662-2826
> 215-662-7903 (fax)
> [log in to unmask]
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Institute of Cognitive Neuroscience &
Wellcome Department of Cognitive Neurology
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