Intercoder Reliability and Validity of WebPlotDigitizer in Extracting Graphed Data

Quantitative synthesis of data from single-case designs (SCDs) is becoming increasingly common in psychology and education journals. Because researchers do not ordinarily report numerical data in addition to graphical displays, reliance on plot digitizing tools is often a necessary component of this research. Intercoder reliability of data extraction is a commonly overlooked, but potentially important, step of this process. The purpose of this study was to examine the intercoder reliability and validity of WebPlotDigitizer (Rohatgi, 2015), a web-based plot digitizing tool for extracting data from a variety of plots, including XY coordinates of interrupted time-series data. Two coders extracted 3,596 data…