Dangers in Visualized Data

Visualized data. That’s graphs, pie-charts and all kinds of creative representations of data. While they make it easier to understand many things, they can also be misleading, write Carl Bergstrom and Jevin West in Calling Bullshit. And not always because of malice or bad intentions…

 

As software makes visual graphics easy, people tend to come up with eye-catching ways of presenting data. Nothing wrong with that, unless…

“The attempt to be cute makes it harder for the reader to understand the underlying data.”

For example, a 3D graph makes it hard to compare the bars: how much taller is the 3rd class bar compared to the 1st class bar? It’s hard to say (visually) since the 1st class bar is farther away and don’t far off objects look shorter than they are? 

Sure, the numerical values are written, but if one has to read it to make sense, then why use a graphic? Even worse, why create an easy-to-misread graphic?

 

Another common error is to show information as circles (no problem with that), which are overlapping. This conveys the impression that we are looking at Venn diagrams. But if it’s not really a Venn diagram, then one may end up drawing wrong conclusions. 


This looks like a Venn diagram, but it isn’t. How can one say that? In a true Venn diagram, the gun owners circle should be contained within the Americans circle.

 

Another easy way to get misled is if the bars in a graph don’t start at zero. 


The graph on the left starts at zero; and one can do a valid comparison of the blue, yellow and red bar heights with each other. The same data is presented in the right-side figure, except it starts at 10, not zero. Therefore, the right-side graph should not be used to compare the bar heights. Yet:

“We may read the numbers on the bars, but we feel the difference in bar heights.”

The feeling that you get of the relative height of the Yellow bar is correct in the left; and very misleading in the right.

 

While visualized data should be easier to understand, at times, it can be misleading. We’d do well to remind ourselves of that.

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