Recent innovations in the changing criterion design: implications for research and practice in special education.

This article illustrates (a) 2 recent innovations in the changing criterion research design, (b) how these innovations apply to research and practice in special education, and (c) how clinical needs influence design features of the changing criterion design. The first innovation, the range-bound changing criterion, is a very simple variation of the classic changing criterion design. The classic version uses a single criterion for each stepwise intervention phase, whereas the range-bound version uses a range criterion--that is, an upper and lower limit for each intervention phase. The second innovation, the distributed criterion, combines elements of the changing criterion, multiple-baseline, and ABAB designs. It is well suited to contexts where students must multitask--that is, allocate, prioritize, and adjust time and effort to complete multiple tasks in response to changing environmental demands. These two innovations expand options available to researchers who use single-case research designs to investigate questions of interest in special education.

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In 1982, Schloss, Sedlack, Elliott, and Smothers published an article in The Journal of Special Education that illustrated "applications of the changing criterion designs to special education classrooms" (p. 361). These applications were based on the classic changing criterion (CC) research design, which Hartmann and Hall (1976) said was "initially named by Hall (1971) and illustrated by Weis and Hall (1971) [and] described, but unnamed by Sidman (1960, pp. 254-256)" (p. 527). For nearly half of a century, researchers have used the CC and other classic single-case designs, particularly the ABAB and multiple-baseline research designs, in special education and other settings. These single-case designs are very useful for evaluating experimental control in studies that (a) include one or a few students; (b) require ongoing, repeated, and quantitative measures of individual students' progress across time; and (c) apply interventions that seek to improve students' performance of socially valid, directly observable, and measurable target behaviors.

Development of Single-Case Designs and Applied Behavior Analysis

In the 1960s, while investigators were developing classic single-case research designs, applied behavior analysis was emerging as a behavior-change technology and as a methodology for evaluating experimental control of interventions that promote intraindividual change over time (Baer, Wolf, & Risley, 1968). Numerous innovations of these classic designs subsequently appeared. According to Hartmann and Hall (1976), "The development of experimental designs to demonstrate control in individual case studies has been a crucial factor in bringing about scientific status to the study of individuals" (p. 527). In many cases, researchers designed these innovations to accommodate their research questions, conditions of the specific intervention and target behavior, and ethical and clinical considerations, or to demonstrate experimental control via visual inspection of graphed data (McLaughlin, 1983).

Kazdin (1982) described numerous variations on the classic single-case research designs, as well as the treatment evaluation strategies and outcome questions that corresponded to these variations. Kazdin concluded, however, that "few variations of the changing criterion design have been developed" (p. 159). During the two decades since Kazdin reached this conclusion, few variations of the CC design have been created (McDougall, 2005b; McDougall, Smith, Black, & Rumrill, 2005). Recently, McDougall (2005a, 2005c) developed and applied two innovations of the classic CC design, which he called the range-bound changing criterion (RBCC) and the distributed criterion (DC). Our purpose in this article is to introduce these two design innovations to the field of special education. We describe how investigators applied these design innovations in the two studies that have used them as of this writing. We show how researchers and practitioners can apply these innovations and associated strategies to special education and illustrate how clinical needs influence design features. First, however, we review the classic CC design and how investigators have used this design to answer questions of interest in special education and related disciplines.

The Classic Changing Criterion Research Design