Characteristics Influencing the Visual Analysis of Single-Subject Data: An Empirical Analysis

A study explored various graphic characteristics associated with the visual analysis of single-subject data. A sample of 20 rehabilitation therapists used visual analysis to rate 24 graphs of data sets using a traditional baseline/treatment (AB) format. Using the intraclass correlation approach, the authors assessed the interrater reliability and found that it ranged from 0.52 to 0.66 for each graph. Data analysis revealed that the graphic characteristics of level and mean shift were associated with consistent judgments across the raters, and that changes in slope across the two phases of a graph were associated with substantial rater disagreement. The authors discuss the implications of using visual and statistical procedures to analyze single-subject data, and argue that quantitative adjuncts to visual analysis may facilitate the reliable interpretation of graphed data for a single subject.