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Thanks Anderson, this makes more sense. Best, Chelsea Chelsea Stillman, Ph.D. NIH/NIMH T32 Postdoctoral Fellow Department of Psychiatry University of Pittsburgh Medical School Primary Appointment: Brain Aging & Cognitive Health Lab <http://www.pitt.edu/~bachlab/LabSite/Home.html/> Commercial Translation Architect, sciVelo <http://scivelo.pitt.edu/people> On Tue, Jul 25, 2017 at 2:24 PM, Anderson M. Winkler <[log in to unmask] > wrote: > Hi Chelsea, > > I think there is a little confusion here: The distribution of TFCE isn't > symmetric around zero, and further, for negative t- or z-stats, it is zero. > So, when you see results in the [0, 0.05] interval (of the 1-p image), it > doesn't mean these results are opposite, or are in the opposite tail. It > just means these p-values aren't significant (i.e., close to 1). This is > even more the case for the corrected map, where the distribution of > p-values under the null is skewed towards 0 (in the 1-p, that is, towards > 1, meaning not significant). > > Hope this clarifies. > > All the best, > > Anderson > > > On 24 July 2017 at 15:43, Chelsea Stillman <[log in to unmask]> wrote: > >> Hi Anderson, Thank you for the response. But do you have any explanation >> for why the effects from the unthresholded maps seem to be in the >> opposite direction from TFCE? In other words, when I open both the >> unthresholded maps (and set z=2.3) and the TFCE maps at 0-.05, they are >> overlapping. >> >> Thanks again, >> Chelsea >> >> >> Chelsea Stillman, Ph.D. >> NIH/NIMH T32 Postdoctoral Fellow >> Department of Psychiatry >> University of Pittsburgh Medical School >> Primary Appointment: Brain Aging & Cognitive Health Lab >> <http://www.pitt.edu/~bachlab/LabSite/Home.html/> >> Commercial Translation Architect, sciVelo >> <http://scivelo.pitt.edu/people> >> >> >> >> On Sat, Jul 22, 2017 at 2:50 PM, Anderson M. Winkler < >> [log in to unmask]> wrote: >> >>> Hi Chelsea, >>> >>> All p-value maps produced by randomise are 1-p, so you'd need to >>> threshold at 0.95. >>> >>> All the best, >>> >>> Anderson >>> >>> >>> On 21 July 2017 at 12:52, Chelsea Stillman <[log in to unmask]> wrote: >>> >>>> Hello, >>>> >>>> We are running randomise on VBM data and want to make sure we are >>>> properly viewing the results: When we open the unthresholded zstat image >>>> and manually provide a minimum height threshold of z = 2.3, we see a fair >>>> number of clusters. Our question arises from the observation that the >>>> clusters that appear in the tfce corrected image thresholded at min of p = >>>> 0 and max of p = .05 overlap with those in the uncorrected z images. >>>> However, the website directions indicate that we should be viewing the tfce >>>> images at a *1-p *threshold of .95 - 1. We have started viewing the >>>> images with a 0-.05 threshold because we noted that the values in the >>>> clusters appeared to be p values (not 1-p values as indicated on the >>>> website). Can anyone confirm whether it is okay to threshold the tfce >>>> output image in this way? >>>> >>>> Thanks in advance for any responses! >>>> chelsea >>>> >>>> Chelsea Stillman, Ph.D. >>>> NIH/NIMH T32 Postdoctoral Fellow >>>> Department of Psychiatry >>>> University of Pittsburgh Medical School >>>> Primary Appointment: Brain Aging & Cognitive Health Lab >>>> <http://www.pitt.edu/~bachlab/LabSite/Home.html/> >>>> Commercial Translation Architect, sciVelo >>>> <http://scivelo.pitt.edu/people> >>>> >>>> >>>> >>> >> >