Dear colleagues,
I am wondering how the expected values shown on the SPM2 output relate to
the SPM results. How the following are defined:
1)- Expected voxels per cluster
2)- Expected number of clusters
3)- Expected false discovery rate
I have searched the mailbase but could not find any clear answer to these
questions.
For instance, in an SPM2 output I got the following after setting voxel
threshold to 0.001 uncorrected and extent threshold to 100 voxels:
1)- Expected voxels per cluster =96.863
2)- Expected number of clusters= 0.77
3)- Expected false discovery rate <=0.42
I know from experience that if I set voxel threshold to 100, the sizes of
the displayed clusters will be at least 100 voxels. But, why I am getting
expected number of clusters =0.77? In this output I have one cluster of
the size 157 voxels and corrected p=0.39 and uncorrected p=0.18.
The expected discovery rate makes sanse as the output shows it. But, how
the expected voxels per cluster and expected number of clusters relate to
the height threshold and extent threshold.
Any reply to this e-mail will be highly appreciated.
Best regards,
Shary
Shahryar Rafi-Tari, M.Sc.
Database Consultant / Imaging Analyst
2075 Bayview Avenue
Sunnybrook & Women's College Health Sciences Centre
Linda C Campbell Cognitive Neurology Research Unit
Room B630
Toronto, Ontario, Canada M4N 3M5
E-mails: [log in to unmask]
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