Biological rhythm experimentation: a longitudinal design and analysis.

Certain experiments exploring the relationship between biological rhythms and external factors such as pharmacologic agents are typified by the particular importance of interaction and conditional effect parameters. The category of biological rhythm experiments presented here also necessarily involves a deliberate confounding of periodicity rooms and biological rhythm stages (time points). These features, together with the longitudinal nature of the observations, require special precautions in the experimental design and analysis.