Friday, December 11, 2009

Misleading graphics undermine your credibility

Look at this graphic from the front page of The Globe and Mail that shows the number of troops involved in four different conflicts.

Which conflict had the most troops involved? If you said the one that takes up most of the visual, you would have come to the immediate conclusion that most people would come to when looking at this visual. But you would be wrong.

The area taken up by the troop icons for the conflict in Afghanistan is the largest area in the visual, representing about three-quarters of the area of the visual. Because we assign proportion based on the proportion of the area representing each item, we incorrectly conclude that this conflict involves the most troops.

If you count the troop icons, again you would conclude that the 135 icons in the Afghanistan conflict part of the visual would represent the largest number of troops since the next highest number of troop icons is 69. Again, this would lead you to an incorrect conclusion.

What the designer did was to use each icon in the Afghan conflict to represent 1,000 troops, but the smaller icons for the other conflicts represent 10,000 troops each. Yes, that is explained in small text below the visual, but most people will not see that explanation. Nor would they easily conclude that a much larger icon represents one-tenth of the smaller icon; it is counter-intuitive.

This is a prime example of a misleading visual. It tries to get you to draw a particular conclusion that is not actually supported by the data. It uses tricks and manipulation to deceive the viewer.

Presenters do this when they manipulate the vertical axis of a graph to show a change to be more dramatic than it actually is. Or when they crop out the part of a photo that gives it context and would cause people to come to a different conclusion. Or when they show only the results that support their point and don’t show data that would enable the audience to get a clear picture of the true situation.

Please don’t do this. Use visuals, but don’t manipulate them. It destroys your credibility and it causes your audience to start to questioning everything you have said. And your presentation is unlikely to be very successful.


Post a Comment

<< Home