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3D Graphs Fool the Viewer’s Eye

Recently, a colleague distributed some rather important health and well-being statistics, illustrating the data with an exploded 3D Graph. Unfortunately, while 3D graphs are more pleasing to the eye than their flat cousins; the perspective necessary to create the 3D illusion, distorts the values being plotted.

Here’s an example using simple arbitrary data. First the exploded version:

 

Pie 3D

Pie Flat

 

 

 

 

 

Notice how, in the 3D version, the Cons wedge appears smaller than the Pros wedge, even though the two wedges represent exactly the same value (46%). In the flat version, on the other hand, the Pros and Cons wedges appear to have exactly the same size.

Is it the Exploded view that creates this illusion? Consider the following unexploded views. The illusion persists.

 

Pie 3D UnexpPie Flat Unexp

 

 

 

 

 

 

 

An unscrupulous presenter could easily use this illusion to distort the facts and unfairly influence his/her audience. (Remember the adage: “Figures don’t lie; liars figure”?) Think about a political race, for example. Depending on which position the presenter wants to improve the apparent advantage of, all he or she has to do is rotate the 3D chart accordingly to immediately improve the apparent advantage of the favoured position:

Pie 3D Unexp

Pie 3D Cons Ahead

 

 

 

The Pros Have It!

The Cons Have It!

Of course, these examples include data labels to help the viewer’s interpretation. Omitting the labels can only make the dishonest presenter’s self-appointed task of deception easier.

So the next time you have to create a graph, think carefully about purpose of graphs and avoid the inevitable optical illusions inherent in 3D charts.

3 Responses to “3D Graphs Fool the Viewer’s Eye”

  • Jordan Goldmeier, a forum member at Linked In Excel Hero Forum made this comment and suggested a helpful link:

    Well, however you feel about pie charts, this little quiz by visualization guru Stephen Few definitely gets you thinking about the best ways to visualize data:

    http://www.perceptualedge.com/files/GraphDesignIQ.html

  • Hervé Thiriez, a forum member at Linked In ExcelKings Forum commented:

    I use to say in my seminars that a 3D chart’s main advantage is to impress a dumb boss. I will now say that they also offer this possibility of cheating…
    Two pros vs. so many cons!

  • Joris Claassen, a forum member at Linked In Excel Enthusiasts Forum commented:

    Unfortunately a lot of people focus on flashy in stead of good informing solutions (charts, websites, …)