Manfred comments on Looking for proof of conditional probability - Less Wrong

-1 Post author: DanielLC 28 July 2011 02:24AM

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Comment author: Manfred 28 July 2011 06:47:55AM 1 point [-]

I think you need the common-sense axioms P(B|B) = 1 and P(A|all possibilities) = P(A). Given these, the Venn diagram explanation is pretty straightforward.

Comment author: DanielLC 28 July 2011 06:22:59PM 0 points [-]

A Venn diagram is not a proof.

Comment author: Manfred 28 July 2011 11:03:50PM 3 points [-]

A series of Venn diagrams, with text explanation, is a perfectly fine proof. The pictures can all be translated into statements about sets. The question is what axioms it starts with about P(A|B).