Dear experts,
For different reasons I found myself double checking the relationship between t-values in t.nii and p-values stored in sig.nii. If I use the following matlab code I thought that I should get the values of my_pval and stored_pval to be the same (except perhaps for the sign):
cd(fullfile(basedir,session,'bold',anal,contrast)) x=load('../X.mat') t=MRIread('t.nii'); sig=MRIread('sig.nii'); test_voxel_number=4000; my_pval=-log10(2*tcdf(-(abs(t.vol(test_voxel_number))), x.DOF)) stored_pval=sig.vol(test_voxel_number)
However I get: stored_pval =
-0.4055
my_pval =
0.2804
Am I doing something wrong here? My FreeSurfer version is 4.5 Thank you!
what is t.vol(test_voxel_number)? Why do you use -(abs(t.vol(test_voxel_number))) instead of +(abs(t.vol(test_voxel_number)))?
doug
Pablo Polosecki wrote:
Dear experts,
For different reasons I found myself double checking the relationship between t-values in t.nii and p-values stored in sig.nii. If I use the following matlab code I thought that I should get the values of my_pval and stored_pval to be the same (except perhaps for the sign):
cd(fullfile(basedir,session,'bold',anal,contrast)) x=load('../X.mat') t=MRIread('t.nii'); sig=MRIread('sig.nii'); test_voxel_number=4000; my_pval=-log10(2*tcdf(-(abs(t.vol(test_voxel_number))), x.DOF)) stored_pval=sig.vol(test_voxel_number)
However I get: stored_pval =
-0.4055
my_pval =
0.2804Am I doing something wrong here? My FreeSurfer version is 4.5 Thank you!
-- Pablo Polosecki Graduate Fellow Laboratory of Neural Systems The Rockefeller University 1230 York Avenue, Box 9 New York, NY 10065
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Douglas N Greve -
Pablo Polosecki