Supersaturated split-plot designs

Methods to construct supersaturated split-plot designs (SSSPDs) are presented. We use an E(s 2)- optimal supersaturated design (SSD) in the whole-plot and half fractions of Plackett-Burman designs (PBDs) in the split plot. It is shown that (1) the resulting split-plot design has orthogonal columns, (2) the split-plot columns are orthogonal to the whole-plot columns, and (3) the whole-plot columns are orthogonal to the whole-plot by split-plot interactions. As an example, an SSSPD is applied to an extrusion process to produce biodegradable packaging foams, and data are analyzed using stepwise selection procedures. It is concluded that SSSPD can be used productively as a screening design when the experiment has a split-plot structure and traditional designs are not feasible.