Bad Decisions with Better Graphics
Does data displayed in charts and graphs, rather than tables, lead to better decisions? Not according to the latest research reported in this month’s Journal of Marketing Research.
The authors looked at various types of biases that creep into business managers’ decisions when based on data presented to them. They did this by conducting experiments with business school students and managers who are members of the American Marketing Association. Some were presented with numeric data in tables, while others were presented with data in charts or graphs. All tables, charts, and graphs were clear and well-designed.
The results? When compared to an optimal decision based on a purely rational assessment of the data, decisions were typically biased, and “graphical formats that followed existing recommendation for the appropriate display of data did not reduce . . . biases compared with data presented in tables.” Moreover, “neither real-world experience nor explicit training reduced these biases.”
In some ways this is surprising, because graphing data can often help us better (and more quickly) grasp its meaning. On the other hand it is not surprising. Graphs can be so visually compelling that they might hinder purely rational assessments.
In our view (and the authors’ as well) the research does not invalidate the need for effective data visualization. A good chart can be a compelling piece of story. But it is not the story, any more than a table of numbers can be the story. A good chart is a communication tool. So are good tables, and so are good sentences that weave together a compelling story.
At Versta Research we use chart and tables in about equal proportions (sometimes tables work better) and we always integrate them into a clear story with appropriate statistical modeling to lend support. The solution to overcoming bias is not fancier graphics, but rather a clear presentation of information with a compelling synthesis and assessment of what it means.
—Joe Hopper, Ph.D.