Dispersion effects from unreplicated designs in the 2(k-p) series

Quality improvement requires reduction of undesired variation. Design of experiments has become a useful tool for discovering such minimum variance conditions, but most existing techniques require a large experimental effort involving replicated experiments. In this article we develop a method for significance testing of dispersion effects from unreplicated two-level fractional factorial experiments using principles close to those for identifying location effects. The method provides an F-distributed test statistic and appears to be useful for identification of dispersion effects as early as the screening stage when fractionated unreplicated experiments are frequently employed.