
a puzzling conditional probability
Posted:
Aug 9, 2012 6:47 AM


Hi,
Given that:
P(AB) = P(notA  notB) = 0.95 and B = 0.05
My goal is to calculate the conditional probability: P(notBA). But how?
I have tried the following to get to the answer... but got stuck at some point, while trying to solve one of the subproblems. Please see below for the details:
It is known that: P(notBA) = P(notB AND A) / P(A)
So, I would need to find P(A), but how? I thought one way to find P(A) would be: P(A) = P(A AND B) AND P(A AND notB)
P(A AND B) is easy to calculate, i.e. P(AB) x P(B) => 0.95 x 0.05 => 0.0475. but how does one calculate the P(A AND notB) ???
Many thanks for help. Regards

