An Interesting Example
During World War II, Abraham Wald worked for the New York company Statistical Research Group. The American military approached him with a problem. War planes were coming back from air battles covered in bullet holes, and the military was interested in protecting future planes by using minimal armour placement. The question was where to best place this armour so as to protect the planes and pilots. The bullet holes were roughly distributed as such:Where would you choose to place the minimal armour?
If you said any section other than the engine section, then you would be absolutely… wrong. Wald’s explanation is as follows: the statistics that were presented were gathered from planes that had survived battle – the planes that didn’t survive battle were not included in the numbers. Thus, the planes that returned were not a random sample and conclusions could not be made by only…
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