How to Make the World Add Up : Ten Rules for Thinking Differently About Numbers

by Tim Harford

First – and most important, since the visual sense can be so visceral – check your emotional response. Pause for a moment to notice how the graph makes you feel: triumphant, defensive, angry, celebratory? Take that feeling into account. Second, check that you understand the basics behind the graph. What do the axes actually mean? Do you understand what is being measured or counted? Do you have the context to understand, or is the graph showing just a few data points? If the graph reflects complex analysis or the results of an experiment, do you understand what is being done? If you’re not in a position to evaluate that personally, do you trust those who were? (Or have you, perhaps, sought a second opinion?) When you look at data visualisations, you’ll do much better if you recognise that someone may well be trying to persuade you of something. There is nothing wrong with artfully persuasive graphs, any more than with artfully persuasive words. And there is nothing wrong with being persuaded, and changing your mind. That’s our next subject.