Selected graph design variables in four interpretation tasks: a microcomputer-based pilot study

Abstract

A pilot study was undertaken to assess the efficacy of selected graph types and information coding schemes in producing quick and accurate graph interpretation. Point-plots, line graphs, bar graphs, and three-dimensional bar graphs were constructed and displayed using an IBM-PC microcomputer with colour monitor. The effectiveness of each of these graph types, as well as the coding scheme used within each (colour versus monochrome), was investigated using 32 subjects in four separate experiments involving either point–reading, point-comparison, trend-reading, or trend-comparison tasks. Dependent measures including task completion time, graph interpretation error, subjective mental workload rating, and graph preference rating were obtained. In three of the tasks, colour-coded graphs were associated with lower task completion time, lower rated mental workload, and higher rated preference than monochrome graphs. However, there were no differences in subjects' error scores between colour and monochrome coding for any of the tasks. For the point-reading task, the three-dimensional bar graphs were less effective than the other graph types, though there were no differences among graph types for the other three tasks. Implications for graph design given specific data interpretation tasks are discussed, based on the results of the four experiments and related literature.