An investigational drug product was studied under sleep laboratory conditions to determine its effect on duration of sleep. A group of 16 patients willing to participate in the study was randomly assigned to one of two drug sequences; 8 were to receive the investigational drug in­period 1 and an identical-appearing placebo in period 2, and the remaining 8 patients were to ­receive the treatment in the reverse order.
a. Identify the design.
b. Give a model for this design.
c. State the assumptions that might affect the appropriateness of this design.