Hi - this default is fairly sensible - it says you want equal probability of false positives vs. false negatives (and is not directly comparable with a p<.05 null hypothesis test - that's a different animal).  For more details on the mixture modelling and alternative hypothesis testing see the various papers by Beckmann and by Woolrich listed on our publications page.

Cheers, Steve.

On 5 Aug 2010, at 14:41, William Sohn wrote:

Dear FSL community,

This is more of a statistical question but I was wondering what the alternative hypothesis test does?  When I run MELODIC on the default setting it says the p>.5.  I was wondering how to interpret it.  Should I be setting this to a much lower setting or is it fine to keep it as is.

Thank you,

-William Sohn

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