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Dear Roman, fslmath's -ptoz option works on actual P-values, and not one-minus-P-values. Does that explain it? -Tom On Fri, Sep 25, 2015 at 2:25 AM, Roman M <[log in to unmask]> wrote: > maybe there is something silly I am missing, but I seem to have an issue > with using the -ptoz option in fslmaths. > > I have run simple Sign Test with randomise and I now want to feed the > output to cluster (which wants a zstat). So, I use the --uncorrp option in > randomise, then type: > > > fslmaths rand_vox_p.nii.gz -ptoz rand_vox_z > > Now, opening the rand_vox_z (i.e., the ptoz image) and the rand_tstat1 > file (also generated by randomise) in fslview it turns out that for most of > the voxels the sign appear flipped between the T and the ptoZ image. > > What happened? In fact, how does ptoz even know what sign to assign to a > given p-value? > > Again, sorry if I'm missing something obvious, but hopefully this will be > easy to answer.. > > Cheers > > R > -- __________________________________________________________ Thomas Nichols, PhD Professor, Head of Neuroimaging Statistics Department of Statistics & Warwick Manufacturing Group University of Warwick, Coventry CV4 7AL, United Kingdom Web: http://warwick.ac.uk/tenichols Email: [log in to unmask] Tel, Stats: +44 24761 51086, WMG: +44 24761 50752 Fx, +44 24 7652 4532