Hi,
A customer has designed an experiment (attached) that includes a 4-level categorical factor, X4, and 3 continuous factors, X1, X2 and X3.
The combination X4 = B and X3 > 0 is not allowed. They used disallowed combinations to ensure that this constraint was obeyed.
However, they would like to estimate the interaction, X3*X4, for the other levels of X4. Is there some way to code the model that would achieve this?
I have tried creating dummy variables for each level of X4 (X4_A ... X4_D) but that is not a very elegant solution.
Thanks,
Phil
If Generalized Regression isn't an option, not sure what other things you can do except break the interaction into 1 df contrasts, which is what you did. Alternatively, you can let Stepwise do it for you. The contrasts will be different and may be less interpretable, though.
Don
