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Hi This is similar to the question in task FMRI of doing multiple comparison correction across different contrasts. The strict answer is that yes, if the 4 tests were all independent then it would strictly be correct to add an extra factor of 4 to the correction. However, a) if they are not independent of each other then this is over-conservative and b) AFAIK no-one actually does do this……. So your reviewer is both right and not so right…maybe Tom has more thoughts on this. Cheers. On 17 May 2011, at 03:33, Bhavani shankara wrote: > Dear FSL list > > We have done TBSS analysis using all Fractional Anisotrophy (FA), Mean Diffusivity (MD), Axial Diffusivity (AD) and Radial Diffusivity (RD), we reported at multiple correction corrected results for all each of these using randomise at statistical significance level of P<0.05 (Corrected for multiple comparison FWE). > > One of the reviewer commenting that we should have used (P<0.05/4= 0.0125 (for each of FA,MD, RD, DA) ) . I think he is suggesting the correction according to Bonfferoni correction. > > My question is, is it sufficient to use p<0.05 FWE corrected for each of the DTI parameters or Should i use the significance level of p<0.0125 on the FWE corrected images as i am doing test for 4 times using FA,MD,RD and AD.. > > Please suggest me and clarify me what is the best statistical significance level to use...? > > Thank you > > -- > Dr. BHAVANI SHANKARA BAGEPALLY > MBBS, (PhD in Clinical Neuroscience) NIMHANS, > Bangalore, > INDIA-560029 > email: [log in to unmask] > --------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------