April 11, 2005 - The Monty Hall Problem

The Monty Hall problem comes up every now and again - it's currently being discussed on the XP mailing list. It's a great problem. The description of the problem is well discussed on the web, so I won't repeat it here.

Everyone I know has who has thought about the Monty Hall problem has got it wrong initially and then, after deeper thought, found the correct answer. The lure of the intuitive answer is so strong for most people (including me), that even after they have read an explanation for the correct answer, they still don't believe it ... everyone has to follow their own road to Damascus ... and everyone finds their own road.

I was so insistent that my intuition was correct that I wrote a little Java program to count the probabilities. It was IntelliJ that opened my eyes. Before I even ran the program, I had a code rule violation.

  open = (guess + 2) % DOOR_COUNT;

"The value assigned to 'open' is never used". Code rules are not just about where you put the curly bracket any more.

Posted by Kevin Lawrence at April 11, 2005 11:03 AM

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Kevin, what is you favorite hint when helping someone understand the problem?

Posted by: David Vydra on August 2, 2005 09:49 PM

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