Crossover Design

The crossover design (also referred to as a replicated Latin square design) refers to a longitudinal study in which participants receive a sequence of treatments that varies based on the group to which the individual is assigned. The groups may be randomly assigned in the case of an experiment or allocated based on some other criteria (e.g., geographic location, classroom) in the case of a nonexperimental study. In its simplest form, the crossover design involves two periods by two treatments. Figure 1 depicts a basic 2 × 2 crossover design with two treatment sequences: AB and BA. As depicted in the diagram, all participants undergo a pretest at the commencement of the study. Then, in the first period of the study, one group of participants ...