Thank you for correcting my rookie mistake, I'll be elaborate henceforth. My dataset consists of response(R) and predictors(a,b,c,d,e) + a categorical predictor(x, which has five groups x1,x2,x3,x4,x5). My regression model is R = const+a(beta1)+b(beta2)+c(beta3)+d(beta4)+e(beta5)+x(beta6)+a*x*(beta7) I want to test for significance of differences between each pair of slopes corresponding to a*x1, a*x2,a*x3, a*x4,a*x5. We will have 10 such pairs ( 5C2). Here's the SAS code that produces a reparametrized model and gives the solutions table for the intercepts and slopes xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx data hye; input a $ b c d e; datalines; /*data goes here*/ ; proc mixed data=hye method=type3; class x; model = b c d a a*x / noint solution; xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Further, I would like to construct the ten contrasts necessary to test for significance of differences between each pair of slopes. I'm completely at loss how to go about it. In case of three contrasts(3C2) originating from 3 groups for a categorical predictor, the code would be like this: ods select SolutionF Contrasts; contrast 'x1 vs x2' a*x 1 -1 0; contrast 'x1 vs x3' a*x 1 0 -1; contrast 'x2 vs x3' a*x 0 1 -1;
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