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Contrasts look good. It really depends on the question you want to answer. The multiple row contrast test whether any of the conditions are significantly different than zero. The single row contrast, tests whether the average effect is significantly different than zero. When you say that F-values are greater. Do you mean the F-values are greater or the p-values are smaller or both? With the global average, the F-values could be greater, but the p-values could also be larger (less significant) due to the different numerator df. On Thu, Jun 4, 2009 at 5:02 PM, John Gelburg <[log in to unmask]> wrote: > Hi all, > > The examples of F-contrast usually show it for one session. I would just > want to make sure that I am OK with defining it for multiple sessions. > Attached experiment design with 8 conditions and 6 sessions. Four first > conditions are different face conditions, whereas 4 remaining conditions > are object conditions. I am interested to see all the regions, where > activation for faces differed from "0" (F contrast). Does it look OK? > > I defined it as: > [1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 > 0 0 0 1 0 0 0 0 0 0 0] > [0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 > 0 0 0 0 1 0 0 0 0 0 0] > [0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 > 0 0 0 0 0 1 0 0 0 0 0] > [0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 > 0 0 0 0 0 0 1 0 0 0 0] > > One more thing: if I define my contrast as simple one line I got much > higher F-values. But is it less correct to make such a grand average? > [1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 > 0 0 0 1 1 1 1 0 0 0 0] > > > Thanks, > John > -- 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.