I am working on a Definitive screening Design (my first) I set design up with 7 factors one of which was a categorical (equipment type) with two levels. When reviewing design with team, request was made to skip step for this equipment two set one of the continous factors to 0.
I am reviewing design now and this change really makes the categorical variable into a 3 level item. I am concerns about issues this may cause with results analysis, and if there are any special steps I should take to modify the design to handle this item?
Any help or suggestions are appriceated.
I am not quite sure what you mean. Could you send the design. If necessary you could create an anonymised version jsut with X1... X7 and coded factor levels (-1,0,1).
That is interesting. So you have a categorical X1 (L1, L2) and a continuous X2 (0, 8000, 16000). And if X2 is 0, then X1 is neither L1 nor L2.
Does it make sense to define X2 as a continous over the range 0 to 16000? After you have run the experiment and modelled the data, will it make sense for the model to make predictions of the response for X2 = 1 or X2 = 500? Would you actually operate in the range 1 to 8000?
Could you change X2 to have a range of 1 to 16000? Or some other range with a lowest setting > 0.