Re: ISI INTERVIEW PREP

Posted by deepak on Jul 03, 2012; 9:21pm
URL: http://discussion-forum.276.s1.nabble.com/ISI-INTERVIEW-PREP-tp7578819p7579020.html

Ok I think I can prove myself wrong :/

I assume independence in the step where I multiply the 2 probabilities ie P(Swap) = P(P1^P2) = P1 * P2

But... I think assuming independence here is wrong. Let's say the 2 events are
E1: Person 1 swaps if he thinks he has a lower number than the other guy ie Y>X
E2: Person 2 swaps if he thinks the same ie X>Y

So, for the 2 events to be independent,
P(E1|E2) = P(E1)
ie P(Y>X|X>Y) = P(Y>X)
but, if it is given that X>Y, then we knwo that P(Y>X|X>Y) is 0, thereby proving the assumption of independence wrong.

So now, how does 1 arrive at the right answer? formally :P