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Hi Helmut,

so, from your point of view, I should only look a the FWE corrected value,
am I right?
Of course, since it is an independent ROI (so it does not correspond a
specific cluster observed at the whole brain level), I can not double check
if that is really really the case, but it makes sense that it is cutting
off some parts of the cluster and thus change the p-value observed.

I would be interested in hearing other people's opinions about that.

Thanks,
Sara



On 9 June 2015 at 15:32, H. Nebl <[log in to unmask]> wrote:

> Dear everyone,
>
> I think the uncorrected cluster p values always refer to properties of the
> whole brain analysis. If your VOI cuts off some parts of a cluster from the
> whole-brain analysis then the uncorrected cluster p value in the results
> table is altered, but this new uncorrected cluster p value is identical to
> the uncorrected cluster p value of another cluster with the same extent in
> the original whole-brain analysis.
>
> In contrast, FWE-corrected cluster p values are adjusted depending on size
> of the VOI and properties of the VOI (sphere, box, or image, they result in
> different calculations).
>
> Thus, corrected cluster p values can indeed become smaller than
> uncorrected ones.
>
> Best
>
> Helmut
>