Optimal Foldover Plans for Two-Level Fractional Factorial Split-Plot Designs

We consider the construction of foldovers of two-level fractional factorial split-plot designs. As a follow-up strategy, the foldover technique is useful when the objective is to systematically de-alias effects of interest after the initial fractional factorial split-plot design has been run. Due to the sequential nature in which the runs of the initial and foldover designs are conducted, the resulting combined design (the design consisting of both the initial design and its foldover) is a blocked fractional factorial split-plot design. Using the minimum aberration criterion for blocked fractional factorial split-plot designs, in conjunction with other optimality criteria, we provide a catalog of optimal foldover plans for initial minimum aberration fractional factorial split-plot designs consisting of 16 and 32 runs.