On the Construction of Trend Resistant Mixed Level Factorial Run Orders

Abstract

In this paper we consider experimental situations where treatments from a mixed level factorial design are to be applied to experimental units over space or time and where there may be an unknown trend effect which can be approximated by some polynomial function of the order in which the observations are obtained. A method of constructing run orders of treatments for such situations is given which generally yields least squares estimators for main effects that have a higher degree of trend resistance than the least squares estimators of main effects that come from run orders obtainable by other methods of construction previously given in the literature.