What is Survivor Bias?
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When you look at something, you usually assume that it’s a typical one of whatever kind of thing it is. There’s way more typical apples than unusual ones, so whatever apple you’re seeing is probably not unusual. Most airplanes are typical airplanes, most people are normal people, etc.
That assumption can be wrong when it’s unusual for this type of thing to be visible to you. If most deer that come near your house get hit by cars, then a deer showing up in your yard is probably unusually good at avoiding cars. If most bullet holes in planes cause the plane to crash, then the bullet holes on the planes that make it home will be unusually far from the vital parts of the plane.
Survivorship bias is the mistake you make when you assume that the things you’re seeing are normal, but they had to be abnormal to be visible to you. If you think normal people can pull themselves out of poverty by their bootstraps because you’ve heard lectures by rich people who did that, or if you think helmets are making soldiers less safe because a lot more came home with head injuries after helmets were added to the uniform, that’s survivorship bias. You’re failing to account for all the people who stayed poor and never got invited to give lectures, and all the soldiers who died of head injuries without helmets but would’ve survived to make it home with them.
Now that you’ve had it explained, you might appreciate [this comic](https://xkcd.com/1827/), which is a joke about survivorship bias.
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