## Details about the wood construction experiment

There were 19 different designs such that main effect estimates of the factors are not affected by active two-factor interactions. Here are the D-efficiencies of the designs with respect to a model with all the main effects and all the two-factor itneractions.

So I chose the first design.

The design has a strength of 3, meaning that, for every set of 3 factors, all combinations occur equally often. An intiguing question is what the advantage of the chosen design is overĀ designs with a better D-efficiency but a smaller strength. I wrote an award winning paper on this subject; see Schoen (2010).