How can I control a DOE 2-level category factor to be in off state 75% of DOE tests?

Question

How can I control a DOE 2-level category factor to be in off state 75% of DOE tests and on state 25% of tests (vs default 50/50)? Thanks in advance - Paul

paul_h_anderson · Answer

Thanks Ryan. I've not used covariates, so I will have to tinker with it some.

I did have another idea. Create a dummy 2-level factor and disallow combinations of factor=on & dummy=on

This would bias the distribution of factor approaching .33 “on” and .66 “off”, but at the expense of an additional factor, driving up the # runs. This only works if I require the dummy factor main & interactions, otherwise it doesn’t strongly drive a bias of state.

Ryan_Lekivetz · Answer

You can manually create a data table with a column having the proportion you want with the desired run size. In Custom Design, select Add Factor -> Covariate, and choose that column. Now you can add the rest of your factors, model terms, etc..., and keep the number of runs the same when creating the design.