DOE: changing Axial Distance for a RSM in Custom design

Question

Hi,

doing a central composite design I can change the axial distance to change the axial points being more within or beyoung the face. Is there something simuilar in Custom Design using a RSM as base? I can do it with augment design too, but not within the custome design.

Thanks,

Martin

Phil_Kay · Accepted Answer

I don't think so, Martin. I can't think of a way to get axial points with Custom Design, other than by augmentation. The reason being that a design with axial points will not be optimal. I guess you could do it with factor constraints? But that would seem like a strange thing to do.

Phil_Kay · Accepted Answer

I recently saw this interesting paper from Cameron Wilden (a good customer of JMP at WL Gore) about adapting optimal design algorithms to create designs with axial points.

martindemel · Accepted Answer

I just tested and also believe creating an i-optimal custom design with interaction effects in the model, then augmenting this design with axial points and center points should work.

Thanks for the reference of the paper, I will check that as well.

Mark_Bailey · Accepted Answer

What about using a Discrete Numeric factor instead of a Continuous factor?

Also, why is it important to have axial points over having an optimal design for the model?