Hi Doug, just to make sure I understand you right: No matter whether I want to test a conjunction a la Friston (any voxel significant, this is what mri_concat gives) or a la Nichols (both voxels significant), I would take the maximum p-value, correct? What about multiple comparisons? Would you threshold the two contrast maps individually, /and or the resulting comjunction map? And if I would like to use cluster size thresholding, how would I get the smoothness estimate for the conjunction map? Thanks, Caspar
2013/5/24 Douglas N Greve greve@nmr.mgh.harvard.edu:
The way to do it is to take the maximum p-value at each voxel (this is what mri_concat does). doug
On 05/24/2013 02:10 PM, Caspar M. Schwiedrzik wrote:
Hi Doug, I am trying to implement something like the MS/CN conjunction suggested by Nichols. For that, I am finding the voxels that show a significant effect at a given threshold in both contrast maps. I have one question about the resulting p-value. In principle, I would tend to think that the conjunction p-value is p-value of contrast1 x p-value of contrast 2, e.g., 0.05*0.05=0.0025. However, one could also think that it is the max of the two p-values. Which one is correct? Thanks, Caspar
2013/5/23 Douglas N Greve greve@nmr.mgh.harvard.edu:
Hi Caspar, I think the 4.x should be the same as 5.x. I'm not sure about your fsfast question. There is nothing to automatically do it (ie, you'll need to run mri_concat) doug On 05/23/2013 03:06 PM, Caspar M. Schwiedrzik wrote:
Hi! I am trying to do a conjunction analysis using mri_concat --conjunct with 2 to three sig.nii as input. It seems to me that the resulting map is what Nichols et al. refer to as MS/GN, i.e., a test against the global null (at least one effect). Is that correct, and does that depends on v4.5 / 5.x? Is there something in FSFAST that would allow me to do a "real" conjunction, that is, all effects significant in a given voxel? Thanks, Caspar _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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