The Effect of Visual Aids on Reading Numeric Data Tables

Data tables are one of the most common ways in which people encounter data. Although mostly built with text and numbers, data tables have a spatial layout and often exhibit visual elements meant to facilitate their reading. Surprisingly, there is an empirical knowledge gap on how people read tables and how different visual aids affect people's reading of tables. In this work, we seek to address this vacuum through a controlled study. We asked participants to repeatedly perform four different tasks with four table representation conditions (plain tables, tables with zebra striping, tables with cell background color encoding cell value, and tables with in-cell bars with lengths encoding cell value). We analyzed completion time, error rate, gaze-tracking data, mouse movement and participant preferences. We found that color and bar encodings help for finding maximum values. For a more complex task (comparison of proportional differences) color and bar helped less than zebra striping. We also characterize typical human behavior for the four tasks. These findings inform the design of tables and research directions for improving presentation of data in tabular form.