Sunday, August 22, 2010

Pr(A|B) /= Pr(B|A)

. Sunday, August 22, 2010

William Easterly on the bias of reverse conditional probabilities:

{People perceive} from media coverage that the probability that IF you are a terrorist, THEN you are a Muslim is high. Unfortunately…{we are confusing} this with the relevant probability, which is the chance that IF you are a Muslim, THEN you are a terrorist (which is extremely low even if the first probability really is high, because terrorists are very rare).

Of course, in the case of the Cordoba House hysteria, the probability that an American Sufi Muslim was a 9/11 attacker is actually zero.

Easterly says that this bias is rampant across issue areas. I can think of many examples off the top of my head.


Pr(A|B) /= Pr(B|A)




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