A METHOD TO IDENTIFY DISPERSION EFFECTS FROM UNREPLICATED MULTILEVEL EXPERIMENTS

The use of experimental design to identify dispersion effects is an ef fective tool for improving quality. In this article the problem of ide ntifying such effects from unreplicated experiments is studied. We foc us on a method developed for two-level 2(k-p) experiments and discuss how the method can be generalized to a wider range of experimental des igns. In particular, we show how dispersion effects can be identified from non-geometric Plackett-Burman designs and from experiments with m ore than two factor levels. In contrast to related methods our approac h provides a test statistic with a well-known reference distribution. Three actual experiments are used to illustrate the method and to make comparisons to related methods. (C) 1997 by John Wiley & Sons, Ltd.