I think you are right I bet you can choose to control FDR locally (clustering?)
2008/8/28 jorge luis <[EMAIL PROTECTED]> > Dear Glen, there is something you have to take into account when using FDR > separately at various regions of a parcelled brain. It do not control de > Global FDR if the null hypothesis is true in many of these regions. > > Although FDR provides strong control of false positives under the null > hypothesis (similar to FWE) you have again a multiple comparison problem. > > See Langers et al. / NeuroImage 38 (2007) 43–56 > > Cheers > > Jorge > > Phd Student > Laboratory of functional Neuroscience. > University of Pablo de Olavide. Seville. Spain > > > --- El jue, 28/8/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> > escribió: > > > De: [EMAIL PROTECTED] <[EMAIL PROTECTED]> > > Asunto: [Freesurfer] Re: FDR correction > > Para: freesurfer@nmr.mgh.harvard.edu > > Fecha: jueves, 28 agosto, 2008 12:37 > > Dear Manja, > > > > It is statistically valid for the threshold suggested by > > FDR to vary in > > the different hemispheres. The reason is that FDR defines a > > proportion, > > not an absolute. The FDR procedure suggests a p-value > > threshold with the > > property that of all positive results at that threshold, > > one can expect > > that no more than X percent are false positives (where X is > > the desired > > FDR rate). It is very possible that the threshold with this > > property would > > be different in the right compared to the left hemisphere. > > > > More informally, one is claiming that of all results > > declared > > "significant", X% are probably B.S. Since X is > > presumably small and the > > number of results large enough to be interesting, one can > > safely conclude > > that the experimental condition explains cortical variation > > at (most of) > > the locations indicated. Now divide the brain into > > subregions (perhaps > > right and left hemisphere, or perhaps something else) in > > each of which X% > > of the significant results are probably false. Then the > > claim that "X% of > > the overall results are probably false" is valid. > > > > > > +glenn > > > > ------------------------------------ > > Here miracles become marvels, and > > marvels recurring wonders. > > -- William Beebe > > > > Dr. Glenn Lawyer > > +352 661 967 244 > > Instituttgruppe for psykiatri > > Seksjon Vinderen > > PB 85 Vinderen > > 0319 Oslo > > http://folk.uio.no/davidgl > > > > > > _______________________________________________ > > Freesurfer mailing list > > Freesurfer@nmr.mgh.harvard.edu > > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > __________________________________________________ > Correo Yahoo! > Espacio para todos tus mensajes, antivirus y antispam ¡gratis! > Regístrate ya - http://correo.yahoo.es > > _______________________________________________ > Freesurfer mailing list > Freesurfer@nmr.mgh.harvard.edu > https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > -- ----------------------------------------------------------- Pedro Paulo de M. Oliveira Junior Diretor de Operações Netfilter & SpeedComm Telecom
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