Survivorship bias

Date created: 2021-09-28

Survivorship bias or survival bias is the logical of concentrating on the people or things that made it past some selection process and overlooking those that did not, typically because of their lack of visibility. This can lead to some false conclusions in several different ways. It is a form of Selection bias.

In world war II, the US military was figuring out which areas of their planes to reinforce. They inspected the planes that returned from missions and could see which areas were most commonly hit. The conclusion was that they should reinforce those areas.

The error here is that they failed to think about the planes that did not make it back. Crucially, the planes that had successfully returned despite taking hits means they probably marked the areas that were not crucial to flight. They should instead reinforce the areas that were unharmed on the planes that returned.