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Dear SPM Users I have some very simple questions regarding the factorial design specification and contrast design for an independent 2-sample t-test with a single covariate. Although many new users have posted on this topic before the replies to their questions do not seem to have made it to the list and therefore I can not find an answer to this question already posted. 1. While building the statistical model: I have 2 groups of 12 participants (control vs. patient) and a covariate of age. Do I need to enter 1 or 2 covariate vectors? What I mean is: Do I enter a vector of control_age (e.g., 32 30 40 25.... 0 0 0 0....) and then a patient_age vector (0 0 0 0..... 24 29 36 39....) or just one vector (32 30 40 25.... 24 29 36 39....)? 2. While defining the contrast do I use simple 1 -1 and -1 1 or do I need to change the definition somehow to include the covariate. My apologies for such a simple question but it does not seem to have been spelled out on the list. Cheers, Deryk Deryk Beal, M.HSc., S-LP(C), Reg. CASLPO Speech-Language Pathologist Doctoral Candidate [log in to unmask] ************************************************************************* This email may contain confidential and/or privileged information for the sole use of the intended recipient. Any review or distribution by others is strictly prohibited. If you have received this email in error, please contact the sender and delete all copies. Opinions, conclusions or other information expressed or contained in this email are not given or endorsed by the sender unless otherwise affirmed independently by the sender.