Graph Comprehension

An Experiment in Displaying Data as Bar Charts, Pie Charts and Tables with and without the Gratuitous 3rd Dimension

by Matthias Schonlau, Ellen Peters

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The authors investigated whether the type of data display (bar chart, pie chart, or table) or adding a gratuitous third dimension (shading to give the illusion of depth) affects the accuracy of answers of questions about the data. They conducted a randomized experiment with 897 members of the American Life Panel, a nationally representative US web survey panel. They found that displaying data in a table lead to more accurate answers than the choice of bar charts or pie charts. Adding a gratuitous third dimension had no effect on the accuracy of the answers for the bar chart and a small but significant negative effect for the pie chart. Viewing the graph/table for less than 8 seconds resulted in less accurate answers. Older age was associated with increased average viewing time (1.2 seconds per 10 years increase in age) but did not affect the accuracy of the answers. Greater numeracy was associated with more accurate answers.

This paper series made possible by the NIA funded RAND Center for the Study of Aging and the NICHD funded RAND Population Research Center.

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