Spotting spurious correlations in health news

When it comes to diet and health, you might see one day that a certain food decreases life expectancy. Then on another day, a different study suggests that food increases life expectancy. It’s hard to know which to believe. David Epstein provides some guidance:

If you’ve watched a lot of NFL games, you’ve probably heard a commentator at some point trot out a stat like: “The Chicago Bears are undefeated in division games following a bye week when they wear their alternate jerseys.”

It is possible that the combination of extra rest and unusual attire gets the Bears amped for division rivals, thus improving their performance — just as it is possible that using the sauna precisely 9-12 times per month at a particular temperature protects against dementia (at first). It is far more likely, however, that given a large database of games and conditions, there will be loads of correlations that occur just by chance; the more you slice and dice the data, the more you’ll find.