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This article is within the scope of WikiProject Mathematics, a collaborative effort to improve the coverage of mathematics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.MathematicsWikipedia:WikiProject MathematicsTemplate:WikiProject Mathematicsmathematics articles
Not sure this is part of the definition of a contrast. It may be a prerequisite for validity in certain contexts, and that may be why the source states this. Japsai (talk) 15:47, 23 September 2008 (UTC)[reply]
I agree. Summing to zero is only required in the classical oneway anova context where the thetas represent groups means. In the more general contexts, where the thetas are arbitrary linear model coefficients, summing to zero may be neither required nor sensible. I have not seen the term contrast used in textbooks outside the classical context, but I have used term term myself in a general linear model context here: https://pubmed.ncbi.nlm.nih.gov/16646809/GKSmyth (talk) 04:11, 28 May 2020 (UTC)[reply]
