A Microsoft Interview Question (aka basic Bayes' Theorem)

[bobbyi]

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Did you take off points, if the applicant pulled out a pen & paper?

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We have whiteboards in our offices and applicants are certainly welcome to try to work out a problem like this on the board. For code/ pseudocode problems, writing the code on the whiteboard is pretty standard. Remember that the point of a problem like this isn't primarily to see what answer the applicant comes up with. It's to see how they think and reason. That means that it would be very silly to penalize someone for doing something that demonstrates how they are trying to arrive at the answer. If you were encouraged to just sit in silence and ponder the question and then blurt out an answer a few minutes later without showing how you came up with it, do you think that would really make for an effective interview process?

[stocktrader23]

I'd guess that I'd just pull the trigger. My simple reasoning being that if you spin it you have a 1/3 chance of landing on death. Considering all safe pulls are in a row I think you have a 1/4 chance since he already went and it was blank. If he had landed on the 1st, 2nd, or 3rd chamber after the bullets you would be safe. 4th one dead.

[reubenf]

Interestingly, if you you hear a *click* when you pull the trigger, your friend's next move it -still- not to spin.

[d10]

I don't know Bayes theorem, and I was tempted to say "Yes, spin it again, obviously your chances of killing yourself now are 2/5, where if you spin it will be 2/6." But the "trick question" flag popped up in my mind so I spent a little more time thinking about it. Then I realized that if you just take a second shot, you will have a 3/4 chance of survival, whereas spinning again reduces it to 2/3.