Depends on your question, the contrast below is comparing group1 to the average of groups 2-4. An alternative is to ask the question: Does group1 differ from group2 OR group1 differ from group3 OR group1 differ from group4? F= [1 -1 0 0; 1 0 -1 0; 1 0 0 -1] Another alternative: Do the groups differ from each other? F=[1 -1 0 0; 0 1 -1 0; 0 0 1 -1] On Thu, Mar 26, 2009 at 11:55 AM, Muhammad A Parvaz <[log in to unmask]>wrote: > hi all, > > we are doing VBM using the VBM5 toolbox and we are doing an ANOVA with 4 > groups. i was wondering what is the correct way to specify the contrast > when > we want to compare one group against the other 3 groups. We are inclined to > use the following weights for our contrast > > [-1 0.33 0.33 0.33] > > is this right? will decreasing the weight of each group to 0.33 change the > signal and variance of that group in anyway? > > Is there a better way to specify this contrast? > > Thanks > -Muhammad > -- Best Regards, Donald McLaren ===================== D.G. McLaren University of Wisconsin - Madison Neuroscience Training Program Office: (608) 265-9672 Lab: (608) 256-1901 ext 12914 ===================== This e-mail contains CONFIDENTIAL INFORMATION which may contain PROTECTED HEALTHCARE INFORMATION and may also be LEGALLY PRIVILEGED and which is intended only for the use of the individual or entity named above. If the reader of the e-mail is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that you are in possession of confidential and privileged information. Any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If you have received this e-mail unintentionally, please immediately notify the sender via telephone at (608) 265-9672 or email.