Single-Case Experimental Designs and Program Evaluation

Abstract

Single-case experimental designs have received little attention in the program evaluation literature. This article provides an overview of single-case methodology, with a specific focus on the A-B-A and multiple baseline designs. The potential utility of these designs for evaluating social programs is discussed, and several examples are provided. Internal validity, statistical conclusion validity, external validity, construct validity, and cost-effec tiveness are considered. Single-case designs offer essentially equivalent protection against threats to experimental validity compared to traditional randomized group designs. It appears that these designs offer, at a minimum, viable methodological alternatives in situations where traditional randomized group designs are infeasible.