Monty Hall

[andrewducker]

[Poll #1770413]

Explanation

I have known what the answer was for ages, but for some reason it only "clicked" in my head today. You can blame sarahs_muse for triggering it.

Comments

[andrewducker]

That's not true.

I know either that I'm in universes 1/3 or in universe 3/4. In either case I have a 50% chance of the other one being male and the other one being female.

[theweaselking.livejournal.com]

Only if you accept "I've checked one and it's female" to mean "I have numbered them, and determined that #1 is female, thus eliminating TWO of the possible results", instead of the intended (and sloppily worded) "I have determined that one of them is female, without caring which"

[andrewducker]

It depends.

Let's assume that there are two doors, each with a raptor behind it.

If they say
"I went behind door 2 and checked, and that one is a female." then we've eliminated two of the results.

If they say "I went behind both doors and checked, and I remember that at least one of them was a female, but I can't remember which one." then we've only eliminated one of the results.

I think this question requires more careful phrasing than the Monty Hall one :->

[chuma.livejournal.com]

"If they say "I went behind both doors and checked, and I remember that at least one of them was a female, but I can't remember which one." then we've only eliminated one of the results."

This example would indeed be a 33% chance of the 3 remaining options.

[theweaselking.livejournal.com]

It does.

But I love this kind of problem because of the *breadth* of the wrong answers you get, and the paths people use to get there.

(I just, here at work, got two more smart educated geeky people to fall for both the Monty Hall and the puppies.)

[chuma.livejournal.com]

I'm sorry but the only wrong answers here are your own. If I could drag others into this argument, I know a statistician who I am sure could explain it more succinctly than I could.

[theweaselking.livejournal.com]

Au contraire, there are at least three wrong answers in the original poll, and at least two wrong answers to the beagle puppies problem. Not counting the two in my office just now!

This is not to say that my answers to this kind of thing are always correct - the Bob And Sue are rolling dice one had me bouncing off wrong answers for hours before I found the trick - but I really do love this kind of problem and this kind of thread because I love seeing *how* people come up with the answers they reach.

[andrewducker]

Yes. Seeing how people's intuitions are broken is always fascinating. Especially when they're mine!

[theweaselking.livejournal.com]

And now you have another example, of mine getting all twisted up!