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Hi Steve, Just wanted to follow up: For which design types is this test appropriate/inappropriate? I've found numerous references to the condition number, but none of them have stated any actual threshold values that are commonly used. How did you arrive at 5e-2? Have you tested simulated data to see how low you could go before the GLM failed? many thanks, jack On Wed, 20 Oct 2004 09:12:23 +0100, Stephen Smith <[log in to unmask]> wrote: >Hi Jack. Yes, the program feat_model (which creates the model given the >design, including outputting the ratio _only if_ it faile test) could be >recompiled to always output this - you just need to find the relevant >printf statement and recompile.... > >The threshold is currently set at 5e-2 - the reason that we have talked >about different thresholds is that doing the test the way we do (via the >ratoi of min to max eigenvalues) isn't appropriate for all design types - >basically it's just more complicated than that. However, we're just now >working on a better test which takes into account the contrasts and >typical noise level etc - so watch this space. > >Cheers. > >On Wed, 20 Oct 2004, Jack Grinband wrote: > >> Hi All, >> What exactly is FEAT's rank deficiency threshold? I searched through the list and various replies >> have listed e(-8), e(-6), e(-5), and e(-4) as "conservative" thresholds. There is 4 orders of >> magnitude between the smallest and largest of these. So, does that mean that the threshold >> depends on some other factors? >> >> Also, I'm having trouble finding the eigenvalue min:max ratio for each analysis. I couldn't find it in >> the log or design files. Is there any way I can get this information? >> thanks, >> >> jack >> > > Stephen M. Smith DPhil > Associate Director, FMRIB and Analysis Research Coordinator > > Oxford University Centre for Functional MRI of the Brain > John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK > +44 (0) 1865 222726 (fax 222717) > > [log in to unmask] http://www.fmrib.ox.ac.uk/~steve