ALTERNATING TREATMENTS DESIGN: ONE STRATEGY FOR COMPARING THE EFFECTS OF TWO TREATMENTS IN A SINGLE SUBJECT

Abstract

A little used and often confused design, capable of comparing 2 treatments within a single [human] subject has been termed a multielement baseline design, a multiple schedule design and a randomization design. The background of these terms is reviewed and a new, more descriptive term, Alternating Treatments Design, is proposed. Critical differences between this design and a Simultaneous Treatment Design are outlined and experimental questions answerable by each design are noted. Potential problems with multiple treatment interference in this procedure are divided into sequential confounding, carryover effects and alternation effects and the importance of these issues, i.e., other single-case experimental designs, is considered. Methods of minimizing multiple treatment interference and methods of studying these effects are outlined. Finally, appropriate uses of Alternating Treatments Designs are described and discussed in the context of recent examples.