Forty years ago, Eugene Edgington developed a single-case AB intervention design-and-analysis procedure based on a random determination of the point at which the B phase would start. In the present simulation studies encompassing a variety of AB-type contexts, it is demonstrated that by also randomizing the order in which the A and B phases are administered, a researcher can markedly increase the procedure’s statistical power.


In the original published version of this article, Panels B and C of Figure 15, p. 38, were reversed, and references to Figure 11 on p. 32 should have referred to Figure 12. This has been corrected.