Hack #71. Think About Frequencies Rather than Probabilities

Probability statistics are particularly hard to think about correctly. Fortunately you can make it easier by presenting the same information in a way that meshes with our evolved capacity to reason about how often things happen.

Mark Twain once said, “People commonly use statistics like a drunk uses a lamppost: for support rather than for illumination.” 1 Things haven’t changed. It’s strange, really, given how little people trust them, that statistics get used so much.

Our ability to think about probabilities evolved to keep us safe from rare events that would be pretty serious if they did happen (like getting eaten) and to help us learn to make near-correct estimates about things that aren’t quite so dire and at which we get multiple attempts (like estimating the chances of finding food in a particular part of the valley for example). So it’s not surprising that, when it comes to formal reasoning about single-case probabilities, our evolved ability to estimate likelihood tends to fail us.

One example is that we overestimate low-frequency events that are easily noticed. Just ask someone if he gets more scared traveling in a car or by airplane. Flying is about the safest form of transport there is, whether you calculate it by miles flown or trips made. Driving is pretty risky in comparison, but most people would say that flying feels like the more dangerous of the two.

Another thing we have a hard time doing is accounting for ...

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