British World War II Bombers – An Example of Why I love Economics

by robekulick

This blog has a very cool story about Abraham Wald, one of the great statisticians, and his work for the British Air Force during World War II (I’m including statistics as part of economics for this entry):

http://www.johndcook.com/blog/2008/01/21/selection-bias-and-bombers/

To summarize the story goes like this:

During WWII the Royal Air Force asked Wald to assess where additional armor was needed on planes based on their data. Wald performed his analysis and came back with a suggestion you might not expect: place additional armor on the spots with the least damage.

If you like puzzles, sit and ponder this for a bit. If you don’t here’s the reason.

Wald realized that the sample of planes for which he had data only reflected those planes which had not been shot down. He then reasoned from there that since bullets can be modeled as hitting a plane randomly, the damaged parts of the planes actually reflected the areas of the planes that were most able to bear enemy fire. The areas that needed the additional armor were the areas that were coming back undamaged because planes being damaged in those areas were not returning!

 

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