Hi all, I'm trying to create a d-optimal main effects design with quantitative variables (e.g. price) that have 3+ levels. In my candidate runs, I observe runs with the intermediate levels of the quantitative variables, however, in all the output for my test designs, I have not seen any runs with intermediate levels of the quantitative variables. Only the largest and the smallest values of those variables.
Has anyone encountered this before, and is there a reason that the d-optimal designs are not selecting runs with the intermediate levels?
Thank you for any advice.
Yes. That is correct. Two points define a line. If you want a linear (quantitative) effect, then the correct behavior is to pick the extreme points. That is most efficient. If you want intermediate points (the middle point for a quadratic effect) then treat the factor as qualitative.
Yes. That is correct. Two points define a line. If you want a linear (quantitative) effect, then the correct behavior is to pick the extreme points. That is most efficient. If you want intermediate points (the middle point for a quadratic effect) then treat the factor as qualitative.
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