In single-case research designs (SCDs) to determine a functional relation a time-series graph is constructed. Preliminary evidence suggest the approach used to scale the vertical axis and the data points per x- to y-axis ratio (DPPXYR) impact visual analysts' decisions. We conducted a systematic review to evaluate time-series graphs published in the last decade in four premier journals in the field of autism. We included 348 articles including 2675 graphs. We identified large variation across and within types of SCDs when evaluating the lengths of the vertical and horizontal axis using the y:x ratio and the DPPXYR, with few adhering to current recommendations. A majority of graphs used an appropriate method to scale the vertical axis that would not increase Type I error rates.
A Decade Review of Two Potential Analysis Altering Variables in Graph Construction