ABSTRACT
Factorial designs, a class of randomized experimental designs, constitute a mature topic in the design of experiments literature. Such designs involve simultaneously studying more than one treatment factors within the same experiment. They were first developed in the context of agricultural experiments, later became quite popular in industrial experiments, and finally found applications in certain types of clinical and behavioral intervention trials. Factorial designs can be used either in confirmatory trials of different treatments for the purpose of efficiency, or in developmental trials to construct optimal multicomponent interventions. In the current chapter, we discuss various usages of factorial design, theoretical background of full and fractional factorial designs, analysis strategies, as well as power and sample size considerations. We discuss real studies employing factorial designs, and present simulation studies to support the discussions.
