Sunday, March 24, 2013

Abraham Wald and statistics

There is a great story about Abraham Wald, the great statistician and measuring the right thing in statistics problem. The Air Force in WWII wanted to determine how they should add armor to their bombers to ensure they would survive. They gathered statistics on all of the bombers that came back after missions and looked at the probability of being hit on certain areas of the plane. The idea was to add armor to those areas most often hit with flak.

They gave their evidence to Prof Wald and asked him to validate their thinking on where to put the most armor. He responded in a very simple way by saying that armor should be placed where there was no record of damage. This was just the opposite of what was expected. His answer was simple, "The bombers hit in those places never came back." 

What an interesting answer to a complex question. This tell us that it is critical to ask the right question. 


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