Recent innovations in small-N designs for rehabilitation research: An extension of Cowan, Hennessey, Vierstra, and Rumrill

This article describes two recent innovations in small-N research design and illustrates how these novel designs apply to research in vocational rehabilitation. The first innovation, the range-bound changing criterion design, is nearly identical to the classic changing criterion except that the former design utilizes a range criterion - that is, an upper and lower limit - instead of a single-point criterion. The second design innovation, the distributed criterion design, incorporates elements of the multiple baseline, reversal, and changing criterion designs. It is well suited to investigations where participants allocate time for multiple tasks and adjust their performance in response to changing environmental demands. By introducing these two recent innovations, this article expands options available to rehabilitation researchers who use small-N research designs.