REFLECTIONS ON VISUAL INSPECTION, RESPONSE GUIDED EXPERIMENTATION, AND TYPE-I ERROR RATE IN SINGLE-CASE DESIGNS

The use of single-case research designs for the evaluation of experime ntal outcomes is a distinguishing characteristic of applied behavior a nalysis. Behavior analysts traditionally rely on visual inspection of graphed data in lieu of statistical analyses. Proponents of visual ins pection claim lower Type I error rates relative to statistical analysi s. However, behavior analysts also employ response guided experimentat ion (i.e., allowing accumulating data to guide the further course of t he experiment). Based on data published by Matyas and Greenwood (1990) , we argue that when visual inspection is combined with response guide d experimentation, Type I error rates could easily be as high as 25%. Tables of error rates as a function of alphas, autocorrelation, and nu mber of looks are presented. We suggest caution in interpreting conclu sions based on single case designs employing visual analysis and respo nse guided experimentation.