These are the basic building blocks of the Stability module and the relationships among them:

A Plan defines a set of events that will occur at specific times for each environmental condition to which units under study are subjected.
A Product is an identifier for units under study.
A Protocol associates one or more Plans with one or more Products.

A Study is a mechanism for executing one or more Plans. A Study applies to only one Product.

Most often, a Study is based on a Protocol. Since the Study applies to only one Product, all Plans for that Product will be executed by the Study.