Economist and maths communicator Tim Harford (previously) presents a riff on Harold Pollack's aphorism that "The best financial advice for most people would fit on an index card," and comes up with a complete set of rules for statistical literacy that fits on a postcard.
Harford's rules: First, interrogate your feelings to discover the bias they're imparting to your perception of a statistic's credibility; next, get the shape of the statistical claim (what's being claimed, what's being left out, what's the causal relationship); next, get the backstory (where did this stat come from?); next, understand the context (is this a "big" number, is it part of a trend, what is its statistical significance?); check your precision (a 50m increase to a number that was in the trillions might be a rounding error); and finally, do a little digging before sharing a stat.
In the end, my postcard has 50-ish words and six commandments. Simple enough, I hope, for someone who is willing to make an honest effort to evaluate — even briefly — the statistical claims that appear in front of them. That willingness, I fear, is what is most in question.
"Hey, Bill, Bill, am I gonna check every statistic?" said Donald Trump, then presidential candidate, when challenged by Bill O'Reilly about a grotesque lie that he had retweeted about African-Americans and homicides. And Trump had a point — sort of. He should, of course, have got someone to check a statistic before lending his megaphone to a false and racist claim. We all know by now that he simply does not care.
But Trump's excuse will have struck a chord with many, even those who are aghast at his contempt for accuracy (and much else). He recognised that we are all human. We don't check everything; we can't. Even if we had all the technical expertise in the world, there is no way that we would have the time.
My aim is more modest. I want to encourage us all to make the effort a little more often: to be open-minded rather than defensive; to ask simple questions about what things mean, where they come from and whether they would matter if they were true. And, above all, to show enough curiosity about the world to want to know the answers to some of these questions — not to win arguments, but because the world is a fascinating place.
Your handy postcard-sized guide to statistics [Tim Harford/Undercover Economist]