Multiple baseline designs: the use of a single-case experimental design in literacy research

Reading Improvement, Winter, 2004 by Richael Barger-Anderson, Joseph W. Domaracki, Nedra Kearney-Vakulick, Richard M. Kubina, Jr.

Weaknesses/Ethical Concerns. When scrutinizing multiple baseline designs, ethical concerns are very seldom an issue generating much discussion (McReynolds & Kearns, 1983: Neuman & McCormick, 1995). One reason is because multiple baseline designs do not withdrawal treatment. In other single-subject experimental research designs (e.g., withdrawal design), treatment is implemented followed by a return to baseline through the removal of the independent variable. For instance, once a students learns how to apply a specific comprehension strategy, the student does not have to unlearn it for the sake of demonstrating a functional relationship.

One area of concern however, is the prolonged nature of baselines. Extended baselines are not always educationally sound for students who need intervention (Neuman & McCormick, 1995). In special education, a student may be behind his same aged peers by a year or more. Some single-case experimental designs allow teachers and researchers the opportunity to immediately implement a treatment (e.g., alternating treatments design) rather than have the student wait in baseline for a protracted period of time.

A further potential weakness of the multiple baseline design is establishing cause-and-effect relationships. Researchers must be aware of causal variables to make statements regarding generality (Dermer & Hoch, 1999). Multiple baseline designs contain potential weaknesses when it comes to proving the effect of the study (Kazdin, 1973). The subsequent phases used to verify that a treatment effect is occurring are done by inference. Inference is demonstrated by the following example: a student whose behavior changes after the independent variable is introduced is an A-B condition (i.e., A is the baseline and B the intervention). The second student also has an A-B condition albeit staggered from the first student. Any subsequent students in later implementation still undergo the A-B condition and the inference is made from all of the data that the effect is due to the intervention.

Another difficult task in the use of the multiple baseline design is choosing dependent variables that are independent of each other. If the dependent variables are not independent of one another, it is not possible to determine the effects of the independent variable. The possibility for the target behaviors to co-vary makes the results of the cause questionable (Hersen & Barlow, 1976: Kazdin, 1973: Neuman & McCormick, 1995). Using a multiple baseline across behaviors with narrative and persuasive writing may result in two behaviors that do not co-vary enough. The effects of the independent variable may not be clearly demonstrated with two similar behaviors.

An additional concern lies in the fact that the participant cannot return to baseline. The multiple baseline design is appropriate to utilize when is not possible or tolerable to return the behavior to baseline (Neuman & McCormick, 1995). However, there are mixed reviews in the literature as to the need for this. For instance, Baer, Wolf, and Risely (1968) have long maintained that a return to baseline is not needed to prove cause-and-effect relationships. On the other hand, there is no way possible to be sure the treatment effects would be the same if the treatment phase came before the baseline phase (Gay & Airasian, 2000; Birnbrauer et al., 1974).