Friday, August 14, 2009

Explain how to interpret unfamiliar graphs before you show them

In a recent consulting assignment, I was reviewing the slides that my client was planning on using for a presentation to a very high-level official in the organization and then to the media. There were four slides that showed the value for each data point and an error bar of two standard deviations. If you don’t know what that would look like, don’t worry. Most people without a statistics background would not understand what it meant. I’m sure it’s no surprise to hear that the slides were created by statisticians.

So what was the problem? The audience would have no idea how to read the graphs. And the entire message would be lost, or even worse, misinterpreted. I suggested that they start that section of the presentation by explaining to the audience how to interpret what they were about to see on the graphs. We enlarged one of the data values and explained what the data point represented and why the error bars were there. Armed with information on how to interpret the graphs, the audience would then read the graphs correctly.

If you have to present graphs that may be unfamiliar to the audience, make sure you first explain how to understand what they are about to see. It may be familiar to you, but those without your background will not understand what you are showing unless you first teach them how to read the graph.


Blogger Richard I. Garber said...


For many people even a logarithmic scale is exotic. I recently heard a talk about the stock market which began by showing the Dow Jones Industrial Average from 1900 to the present, as is shown here:

The vertical scale was logarithmic, but the speaker didn’t explain that at first. I saw a lot of puzzled looks and frowns in the audience.

Later on in the speech he said a log scale was a good way to display data over a wide range of values. A few words before showing that graph should have explained that the vertical scale used equal intervals for each factor of ten. Then he could have brought the audience along instead of losing them.


1:13 PM  
Blogger JTstag said...

Even with simple graphs, presenters often fail to design it in such a way that the audience understands what the point of showing the data is. Which data point is most important? Should we care about the time? Using contrasting colors (red vs. grey) is a great way to steer the audience's attention to the important information. Of course, as you state in your post, if the graph is so complicated that the audience can't understand it, no amount of color will matter.

9:41 PM  

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