Changing-criterion design refers to a small-n design in which the criterion to obtain some outcome changes systematically over time. It is a type of single-subject design in which the effect of the treatment is demonstrated by how closely the behavior matches a criterion that is systematically altered.
Moreover, Changing-criterion design is a single-subject design consisting of a series of phases, each phase defined by a specific criterion that determines a target level of behavior. The criterion level is changed from one phase to the next.