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LLN, le 25/02/05 Dear All, I'll be happy to hear our stat gurus on the contrasts proposed by Caroline. >For the 1st level analysis, the following t- contrasts are created: > > 1. [-1 1 0] for A vs Rest > 2. [-1 0 1] for B vs Rest > 3. [0 1 0] for condition A > 4. [0 0 1] for condition B My understanding was that, as all conditions are explicitely declared, contrasts 3 and 4 that are "conceptually" equivalent to 1 and 2 should not work because, as they do not sum to 0, there is nothing left for SPM to compare them. I thought that 3 and 4 would work only if Rest had not been explicitely declared. Am I right or wrong? > I know I am comparing different things in the 2nd level analysis, >but what exactly are the differences between theses 6 comparisons? >How to do a correct ANOVA? If A and B are in the same run/session, there is maybe no need to compare them through Rest. You could compute A-B at the 1st level and take these con* files to the second level in a one-sample t test. (Right?) Yours, Mauro. -- _____________________________________ Help fighting hunger: http://www.hungersite.com Just click your mouse and sponsors of The Hunger Site donate a serving of food to a person in need - at no cost to you. ______________________________________ Mauro PESENTI Research Associate, National Fund for Scientific Research (Belgium) Unite de Neurosciences Cognitives Departement de Psychologie Universite Catholique de Louvain Place Cardinal Mercier, 10 B-1348 Louvain-la-Neuve tel.: +32 (0)10 47 88 22 fax: +32 (0)10 47 37 74 E-mail: [log in to unmask] http://www.nesc.ucl.ac.be http://www.nesc.ucl.ac.be/mp/pesentiHomepage.htm