Crossover trials with a cumulative response

We consider the use of a crossover design when the response is long-lasting and cumulative. Examples include the treatment of chronic diseases such as cerebral palsy, and educational and psychological intervention studies. Cumulative response models are developed for the two-treatment, two-period design. Various estimators for the treatment and carryover effects are compared, and ANOVA tables are derived. The crossover design including pretreatment observations is found to be more cost-efficient than the one-period randomised design. Without pretreatment data, it may be more or less efficient, depending on the reliability of the data, and the costs of subject recruitment, treatment, and observation.