A Decade Review of Two Potential Analysis Altering Variables in Graph Construction
Single-case research designs (SCRDs) are used to evaluate functional relations between an independent variable and dependent variable(s). When analyzing data related to autism spectrum disorder, SCRDs are frequently used. Namely, SCRDs allow for empirical evidence in support of practices that improve socially significant outcomes for individuals diagnosed with ASD. To determine a functional relation in SCRDs, a time-series graph is constructed and visual analysts evaluate data patterns. Preliminary evidence suggest that the approach used to scale the ordinate (i.e., y-axis) and the proportions of the x-axis length to y-axis height (i.e., data points per x- to y-axis ratio) impact visual analysts’ decisions regarding a functional relation and the magnitude of treatment effect, resulting in an increased likelihood of a Type I errors. The purpose for this systematic review was to evaluate all time-series graphs published in the last decade (i.e., 2010-2020) in four premier journals in the field of ASD: Journal of Autism and Developmental Disorders, Research in Autism Spectrum Disorders, Autism, and Focus on Autism and Other Developmental Disabilities. The systematic search yielded 348 articles including 2,675 graphs. We identified large variation across and within types of SCRDs for the standardized X:Y and DPPXYR. In addition, 73% of graphs were below a DPPXYR of 0.14, providing evidence of the Type I error rate. A majority of graphs used an appropriate ordinate scaling method that would not increase Type I error rates. Implications for future research and practice are provided.