There are no easy charts

The snow made me do it - California, here I come

Light entertainment: another use of the scatter plot

There are no easy charts

Feb 05, 2015

Every chart, even if the dataset is small, deserves care. Long-time reader zbicyclist submits the following, which illustrates this point well.

The following comments are by zbicyclist:

This is from http://win.niddk.nih.gov/statistics/ -- from the National Institute of Diabetes and Kidney Diseases, part of the U.S. National Institutes of Health.

The pie chart is terrible in a pedestrian way – a bar chart could be so much clearer, or even a table. You have to do too much work to match up the colors, numbers and labels on the pie chart.

To the right of the pie is a bar chart, but a bar chart in which the categories are nested – extreme obesity is part of obesity, extreme obesity and obesity are part of overweight or obesity. If we want to do something like this, there should be 3 charts (e.g. space on the x axis indicating a break). The normal expectation for a bar graph is that the categories are mutually exclusive. This problem is repeated in the Race/Ethnicity graph just below these.

***

Now, some comments by me.

Another issue of the design is inconsistency. The same color scheme is used in both charts but to connotate different concepts.

Put yourself at the moment when you just understood the chart on the left side. You figured out that obesity is deep green while extreme obesity is light green. Now you shifted your attention to the column chart. You were expecting the light green columns to indicate extreme obesity, and the deep green, obesity. And yet, the light/dark green represents a male-female split.

Here is a stacked column chart showing that females are more likely than males to be either extremely obese or not overweight. In other words, the female distribution has "fatter tails".