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Use an F-Contrast: [1 -1 0 ; 0 1 -1] If this is significant, you can then evaluate the following t-contrasts: [1 -1 0] [1 0 -1] [0 1 -1] and the reverse contrasts: [-1 1 0] [-1 0 -1] [0 -1 1] Keep you eyes on the list to see if anyone responds about how to correct for the fact that you are doing 3 post-hoc tests, which inflates the type 1 error. Best Regards, Donald McLaren ================= D.G. McLaren, Ph.D. Postdoctoral Research Fellow, GRECC, Bedford VA Research Fellow, Department of Neurology, Massachusetts General Hospital and Harvard Medical School Office: (773) 406-2464 ===================== 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 (773) 406-2464 or email. On Fri, Sep 16, 2011 at 12:58 AM, Adam Felton <[log in to unmask]> wrote: > I apologize in advance for asking such a simple question, but I couldn't find the direct answer in the archives and I couldn't figure it out from the ANOVA pdf's that have been previously recommended. > > How do I set the contrast weights to compare three groups with a one-way between-subjects ANOVA? > > I am comparing three groups (people who score better at task 1; people who score better at task 2; people who are equal at both tasks). I've seen it previously recommended that [1 -1 0] be used; is that equivalent to [-1 1 0] or [0 -1 1], etc? > > > Thank you for your help, > > > Adam >