Critical Values of the Lenth Method for Unreplicated Factorial Designs

Abstract

AbstractThe Lenth method is an objective method for testing effects from unreplicated factorial designs and eliminates the subjectivity in using a half-normal plot. The Lenth statistics are computed for the factorial effects and compared to corresponding critical values. Since the distribution of the Lenth statistics is not mathematically tractable, we propose a simple simulation method to estimate the critical values. Confidence intervals for the estimated critical values can also easily be obtained. Tables of critical values are provided for a large number of designs, and their use is demonstrated with data from three experiments. The proposed method can also be adapted to estimate critical values for other methods.KeywordsConfidence IntervalsExperimentwise Error RateIndividual Error RateFactorial DesignsFractional Factorial DesignsMixed-Level DesignsPlackett-Burman DesignsSimulation Additional informationNotes on contributorsKenny Q. YeDr. Ye is an Assistant Professor in the Department of Applied Mathematics and Statistics. His email address is kye@ams.sunysb.edu.Michael HamadaDr. Hamada is a Technical Staff Member in Statistical Sciences.