Optional analyses of crossover trials having two treatments and a placebo

Abstract

The assumption of carryover effects is unavoidable due to the very nature of crossover designs. Even in case of crossover design with washout period, the hypothesis of no carryover effect should be tested and established. On the other hand, this assumption makes the analysis difficult and potentially biased or inefficient in case of two treatment two period crossover design. For a reasonable estimation, experimenters are advocated to employ a two period three treatment crossover designs, or a three period two treatment crossover design. In this article, we present optional analyses of a uniform three period three treatment crossover design, consisting of a placebo and two active treatments. We develop a test for detecting presence of carryover effects which directs experimenter for a proper analysis of his crossover trial. We present ANOVA for each of the three possible carryover models, that both, single, or none of the active treatments has carryover effect, and illustrate through an example.