The Data Detective: Ten Easy Rules to Make Sense of Statistics

by Tim Harford

In the first chapter, I advised trying to notice your feelings about the claim; in the second chapter, constructively sense-checking the claim against your personal experience; in the third chapter, asking yourself if you really understand what the claim means. These are all simple, commonsense suggestions, and in this chapter I’ve added a fourth: Step back and look for information that can put the claim into context. Try to get a sense of the trend. “Another terrible crime has occurred!” is perfectly consistent with “Overall, crime is way down.” Look for something that will give you a sense of scale, such as comparing the situation in one country with the situation in other countries, or figuring out the cost per person of some proposed government expenditure. None of these methods is technical; anyone can use them. Together they can go a long way toward providing statistical illumination. But sometimes we need to dig a little deeper into how a statistic was produced.