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It is explained correctly. There are two doors with goats, and he opens one of them randomly if you didn't pick one of them. Note that he explains it twice; t
by kd5bjo 16y ago
It is explained correctly. There are two doors with goats, and he opens one of them randomly if you didn't pick one of them. Note that he explains it twice; the first time with the common logic error that he tends to make and the second correctly.
- JoeAltmaier 16y agoWhether Monty opens a door or not doesn't change your probability - the door you chose has 1/3 chance. Wave your hands all you want and show off bogus math if you like.
- JoeAltmaier 16y agoOk, smart guys. Imagine Monty didn't have any "probability" of opening a "goat door": he just opens the 1st one (or only one if he only holds 1). It doesn't change anything about the problem; but that fake math quits working.
- gwillen 16y agoI almost believed you, until I ran through this version of the problem, and realized that, if I know Monty always opens the lower-numbered goat door, it actually gives a completely different result. In particular, if I pick door 2, and Monty picks door 3, this _guarantees_ that the car is behind door 1 under your version of the problem. Meanwhile, if I pick door 2, and Monty picks door 1, it is now 50/50 whether I should switch or not, instead of 2/3 to 1/3. Try the math yourself and see. So the reason the "fake math" quits working is that you've changed the problem; if you do the math using the method at the link, for your version of the problem, you _rightly_ get different results, and I believe they are correct.
- JoeAltmaier 16y agoNot quite. You may have picked the right door all along. It clearly doesn't matter then which door Monty opens, since they both show goats.