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Georgios, just to add to Matthew's answer: the reason raw TFCE is not enough to reject an H0 is that it does not have a known/epxected (a piori) distribution, such as T or Z, so that you can take TFCE value and convert it into a P-value. Therefore, for the inferene on a TFCE value, you need a permutation-based-generated H0, i.e., a nonparametric inference ... In order to have the TFCE image, you can either use -R option in randomise command OR feed your T-stat image to fslmaths, which can convert it to a TFCE image given E, H and connectivity parameters . Cheers On Thu, Jul 22, 2010 at 2:10 PM, Matthew Webster <[log in to unmask]>wrote: > Hello, > The raw statistic contains the TFCE scores for the > unpermuted-data ( permutation 1 ). By permuting, randomise is able to > generate the null-distribtution for these TFCE scores and so calculate > p-values for the original ( raw ) statistic image. It is mostly far more > appropriate to present these p-values than the raw TFCE-scores. > > Many Regards > > Matthew > > > Hello TBSS experts, > > > > I have a question concerning how valid it is to present raw test > statistics. > > > > After running randomise I get the three following thresholding/output > options: > > a) _tfce_corrp_tstat (FWE - TFCE corrected for multiple comparisons) > > b)_tfce_p_tstat (TFCE - uncorrected for multiple comparisons) > > c)_tfce_tstat (TFCE - raw test statistic) > > > > In the literature, it is common that both corrected and uncorrected TBSS > results (voxel-wise and TFCE) are presented with the latter validation of an > application of a ROI analysis, in the regions identified as having > statistically significant differences. > > > > So my question is, can one present these _tfce_tstat (TFCE - raw test > statistic) results and use a ROI analysis to back them up or is this > inappropriate? > > > > Additionally, could someone please point me in the right direction as > where to read up on these "raw test statistics" because I can't find any > information in the archives or in the randomise manual. > > > > Thank you for your insight and help, > > > > Georgios Alexandrou M.D. > > Karolinska Institute > > Astrid Lindgren Children's Hospital, > > Stockholm, Sweden > > > -- Reza Salimi-Khorshidi, DPhil Candidate, Dept. of Clinical Neurology, University of Oxford (Linacre College). [log in to unmask] FMRIB Centre, John Radcliffe Hospital, Oxford OX3 9DU Tel: +44 (0) 1865 222704 Fax: +44 (0)1865 222717