Fort Fun Indiana
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- Mar 10, 2017
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The simple brilliance of Darwin's revelation
This revelation was natural selection. Evolution appeared, to Darwin, to be a fact that explained the existence of every organism on the planet. And a mechanism to explain this fact was proposed by Darwin: natural selection. But how did Darwin puzzle this out?
By the simple brilliance of recognizing "survivorship bias". Survivorship bias causes us to miss the forest for the trees.
My favorite illustration of this -- for its simplicity -- is Abraham Wald's (who coined the term "survivorship") analysis of how best to armor our bombers during WW II. He was presented with the following information, which shows where returning bombers were hit by enemy strikes:
Without recognizing survivorship bias, one might think that the (limited resource, have to conserve weight) armor should be increased in the spots where the bullet holes are concentrated. This would seem to be where most bullet strikes occur, per the data. So more armor should be spent in those places, right?
No. One would better spend the armor on the places where returning planes show fewer strikes. Why? Because the bombers that were hit in those areas did not make it back. They splashed.
Darwin's revelation of natural selection owes itself to the same turn of thought. The other models that are not observed? They died off, and the more successful models propagated instead. That being the case, selection bias would greatly influence what we observe today.
Darwin's answer to the cause of that bias was the brilliant idea of natural selection.
This revelation was natural selection. Evolution appeared, to Darwin, to be a fact that explained the existence of every organism on the planet. And a mechanism to explain this fact was proposed by Darwin: natural selection. But how did Darwin puzzle this out?
By the simple brilliance of recognizing "survivorship bias". Survivorship bias causes us to miss the forest for the trees.
My favorite illustration of this -- for its simplicity -- is Abraham Wald's (who coined the term "survivorship") analysis of how best to armor our bombers during WW II. He was presented with the following information, which shows where returning bombers were hit by enemy strikes:
Without recognizing survivorship bias, one might think that the (limited resource, have to conserve weight) armor should be increased in the spots where the bullet holes are concentrated. This would seem to be where most bullet strikes occur, per the data. So more armor should be spent in those places, right?
No. One would better spend the armor on the places where returning planes show fewer strikes. Why? Because the bombers that were hit in those areas did not make it back. They splashed.
Darwin's revelation of natural selection owes itself to the same turn of thought. The other models that are not observed? They died off, and the more successful models propagated instead. That being the case, selection bias would greatly influence what we observe today.
Darwin's answer to the cause of that bias was the brilliant idea of natural selection.
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