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Hi - upsampling/resolution should not affect the validity of randomise p-values, regardless of the test statistic. Cheers. On 7 Mar 2013, at 15:19, alberto corcoba wrote: > Dear FSL team, > > I am trying to run the TBSS analysis on mice FA data. My problem is that I have in vivo scans with non-isotropic 0.3*0.15*0.6mm voxels. At this resolution, some upsampling of the images was necessary to get the tbss_skeleton script to build a skeleton with reasonable similarity to the underlying anatomy. (I've compared it to what Ruest et al. published in 2011 in NMR in biomedicine using high-res isotropic data). > My question is: how will upsampling affect the statistical results?. I am comparing wild-type to knock-out mice (2 groups unpaired t-test). > I have been through the Smith & Nichols Neuroimage paper on TFCE and I understand that if the extension of the significant clusters to be fed into the TFCE algorithm is given in # of vxls, then upsampling will influence the output, whereas if it is given in mm3 it won't (that much?). > Can somebody give me some help with this? > > Thanks a lot in advance, > > Alberto > > .-- > Alberto Corcoba > > Centre d'Imagerie BioMédicale > EPFL - LIFMET > Station 6 > 1015 Lausanne, Switzerland > +41 (0) 21 69 30586 > --------------------------------------------------------------------------- Stephen M. Smith, Professor of Biomedical Engineering Associate Director, Oxford University FMRIB Centre FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) [log in to unmask] http://www.fmrib.ox.ac.uk/~steve ---------------------------------------------------------------------------