Recognize that software defaults may be problematic

Example-3_figure-1

This column graph was part of a slide set used for a presentation to physician researchers by a representative from a large, multinational information company. The chart has been redrawn and the text scrubbed of identifying information.

 

When users decode a column graph, they make judgments about the comparative heights of the columns, a comparison we can make quite accurately. However, height is only accurately depicted if the baseline is zero.

Differences between the four categories in this column graph are exaggerated by the use of a nonzero baseline.

The column graph immediately below accurately depicts the information.

Example-3_figure-2

When I first encountered the original graph, my initial thought was that the designer intentionally constructed the column graph to be deceptive. Then, I put the numbers into a Microsoft Excel spreadsheet and created a column graph within Excel.

Excel default

The column graph in the slide set appears to have been constructed using a default setting in Excel.

Relying on the default settings of graphing software programs is problematic and may result in improperly constructed, difficult to interpret, and potentially misleading graphs.

See the difference?

Example-3_figure-3