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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] Disclaimer: This e-mail is intended for the addressee(s) only, and may also be confidential. Any review, retransmission, or other use of this information by persons other than the addressee is strictly prohibited. If you are not the addressee or received this by mistake, please contact the sender and delete the material from all your computers.