How to fail three tests in one chart

November 12, 2012
By

(This article was originally published at Junk Charts, and syndicated at StatsBlogs.)

The November issue of Bloomberg Markets published the following pair of pyramid charts:

Bb_pyramids

This chart fails a number of tests:

Tufte's data-ink ratio test

There are a total of six data points in the entire graphic. A mathematician would say only four data points, since the "no opinion" category is just the remainder. The designer lavishes this tiny data set with a variety of effects: colors, triangles, fonts of different tints, fonts of different sizes, solid and striped backgrounds, and legends, making something that is simple much more complex than necessary. The extra stuff impedes rather than improves understanding. In fact, there were so many parts that the designer even forgot to add little squares on the right panel beside the category labels.

Junk Charts's Self-sufficiency test

The data are encoded in the heights of the pyramids, not the areas. The shapes of the areas are inconsistent, which also makes it impossible to decipher. The way it is set up, one must compare the green, striped triangle with two trapezoids. This is when a designer realizes that he/she must print the data labels onto the chart as well. That's when self-sufficiency is violated. Cover up the data labels, and the graphical elements themselves no longer convey the data to the readers. More posts about self-sufficiency here.

Junk Charts's Trifecta checkup

The juxtaposition of two candidates' positions on two entirely different issues does not yield much insights. One is an economic issue, one is military in nature. Is this a commentary of the general credibility of the candidates? or their credibility on specific issues? or the investors' attitude toward the issues? Once the pertinent question is clarified, then the journalist needs to find the right data to address the question. More posts about the Trifecta checkup here.

Minimum Reporting Requirements for polls

Any pollster who doesn't report the sample size and/or the margin of error is not to be taken seriously. In addition, we should want to know how the sample was selected. What does it mean by "global investors"? Did the journalist randomly sample some investors? Did investors happen to fill out a survey that is served up somehow?

***

The following bar charts, while not innovative, speak louder.

Redo_pyramid1
Redo_pyramid2



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