Reply-To: | | [log in to unmask][log in to unmask]] On Behalf Of Thomas Nichols > Sent: Sunday, June 01, 2008 4:28 PM > To: [log in to unmask] > Subject: Re: [SPM] SPM 5 VBM: FWE/FDR errors > > Dear Megan, > > This sounds very strange, as FWE and FDR calculations are > quite different. > > Can you clarify exactly what you enter ('0.05' ?) and in > response to exactly which question? > > Also not that you say 'cluster = 100', but that's just an > arbitrary number (all clusters smaller than 100 are omitted) > and not a specific FWE-level threshold. FWE cluster > inferences are read off of the table for any uncorrected > threshold you give SPM. > > -Tom > > > > On Fri, May 30, 2008 at 2:56 PM, Megan Walsh <[log in to unmask]> wrote: > > > Hey fellow SPM-ers- > > I am currently doing a multiple regression analysis on > some VBM data. I understand that cluster-wise thresholding > is certainly not ideal for multiple comparison corrections. > To correct for multiple comparisons I wanted to specify my > FWE as p<0.05. When I specify this I get the following error message: > > ??? Error using ==> betainc at 42 > X must be in the interval [0,1]. > Error in ==> spm_Tcdf at 106 > F(Q) = xQxPos > -(xQxPos*2-1).*0.5.*betainc(v(Qv)./(v(Qv)+x(Qx).^2),v(Qv)/2,1/2); > Error in ==> spm_P_RF>spm_ECdensity at 157 > EC(1,:) = 1 - spm_Tcdf(t,v); > Error in ==> spm_P_RF at 59 > EC = spm_ECdensity(STAT,Z,df); > Error in ==> spm_uc_RF at 47 > p = spm_P_RF(1,0,u,df,STAT,R,n); > Error in ==> spm_uc at 39 > u = spm_uc_RF(a,df,STAT,R,n); > Error in ==> spm_getSPM at 602 > u = spm_uc(u,df,STAT,R,n,S); > Error in ==> spm_results_ui at 274 > [SPM,xSPM] = spm_getSPM; > ??? Error while evaluating uicontrol Callback > > The same idea goes for the FDR correction. However, if > I cluster threshold it works fine (cluster=100). > Can anyone help me figure out how to either a) fix the > problem, or b) an alternative manner in which I can correct > for multiple comparisons? > > Thanks, > Meg > > -- > Megan Kay Walsh > Graduate Student > Johns Hopkins University > Psychological & Brain Sciences > 204 Ames Hall > 3400 N. Charles St. > Baltimore, MD 21218 > > > > > -- > ____________________________________________ > Thomas Nichols, PhD > Director, Modelling & Genetics > GlaxoSmithKline Clinical Imaging Centre > > Senior Research Fellow > Oxford University FMRIB Centre >35_2Jun200809:31:[log in to unmask] |