Hello, I intend to test a interaction between two variables, but not via multiplicative interaction variable (e.g., Y = beta0 + beta1*X1 + beta2*X2 + beta3*X1*X2). My GLM model is Y = beta0 + beta1*X1 + beta2*X2. After the PROC GLM I got the estimation of beta1 and beta2 with their 95% confidence intervals. Both X1 and X2 are binary variables, means they either can be 0 or 1, respectively. Now I want to estimate the interaction contrast (additive interaction instead of multiplicative one), defined as, Interaction contrast = Y11 - Y01 - Y10 + Y00, and to compare it with ZERO. It would be better to have its 95% confidence interval. However, I don't know how to. Thanks.
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