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Re: conjunction analysis at second level

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Wed, 2 Apr 2008 12:41:38 +0100

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 ```[log in to unmask] wrote: > Dear Will, > > How are you? > > I have a question regarding how to do conjunction analysis on the > second level. Hope you can help me out. thanks! > > I had one group subjects who performed 3 tasks (A,B and C). In each > task, they had 2 conditions (C and I) for both uncrossed (u) or > crossed (c) hands, so totally four conditions which were uC, uI, > cC,cI in each task and it was a 3*2*2 factorial design. In the first > level, I have specified the contrasts, such as uI-uC, cI-cC, > (uI+cI)-(uC+cC) and (cC+cI)-(uC+uI) for each task. Now I want to do > conjunction analysis in the second level,e.g where is the common > activation of uI-uC for the three tasks? When I clicked on the second > level, which one I should select, full factorial or flexible > factorial design? I guess I don't need to use one-sample or > two-sample design. Thanks! > For each subject generate three contrasts. These will be uI-uC for each of the three conditions. At the second level select a full factorial design. Then create a single factor with three levels. Your design will be a one-way ANOVA with three levels. You'll have three columns in your design matrix - one for each condition. After estimating the model parameters, select the three contrasts (select multiple contrasts by pressing the control button - or is it shift, shift/control I forget) [1 0 0], [0 1 0] and [0 0 1]. Best wishes, Will. > Regards, -- William D. Penny Wellcome Trust Centre for Neuroimaging University College London 12 Queen Square London WC1N 3BG Tel: 020 7833 7475 FAX: 020 7813 1420 Email: [log in to unmask] URL: http://www.fil.ion.ucl.ac.uk/~wpenny/ ```