On the Robustness and Efficiency of Some Randomized Designs

Abstract

A concept of model-robustness is defined in terms of the performance of the design in the presence of model violations. The robustness problem is discussed for several randomization procedures commonly used in experimental design situations. Among them, the balanced completely randomized design, the randomized complete block design and the randomized Latin square design are shown to be model-robust in their own settings. To compare different randomization procedures, we define a concept of efficiency which depends on the particular "pattern" of model violations. This concept, when applied to different designs, gives results which are consistent with the intuitive grounds on which the designs are suggested.