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Subject: Re: New and final solution of the Monty Hall Dilemma *Conclusion*

Author: Sune Fischer

Date: 04:58:01 09/27/02

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On September 27, 2002 at 07:24:42, Rolf Tueschen wrote:

>On September 27, 2002 at 07:15:52, Sune Fischer wrote:
>
>>On September 27, 2002 at 06:57:57, Rolf Tueschen wrote:
>>>>This depends on what the candidate knows about the host, if he knows the host
>>>>knows, then he should expect 2/3 chance by switching
>>>
>>>Yes. But exactly that was the revealation I made. No big science at all, just a
>>>careful analysis of the historic data about Marilyn vos Savant. Nothing more
>>>nothing less. Please don't feel offended that I presented the case here in
>>>computer chess, I thought it could help many people to be more careful in stats
>>>and conclusions.
>>>
>>
>>Yes, but it is a little confusing because there are two 'you's there.
>>There is the "you" on stage that may know nothing, and the "you" who should
>>answer the question on behalf of the "you" on the stage.
>>
>>It is not clear what the "you" on stage knows about the host, i agree with that.
>>
>>But I don't see what it has to with doors opening or not, that must be a
>>different question I think.
>>
>>>.
>>>>
>>>>>In special the
>>>>>candidate could _not_ know if the host had opened a further door because he knew
>>>>>that no car was behind it. The text of the question does not allow to make a
>>>>>different conclusion. QED)
>>>>
>>>>But since you are the one that makes the decision, and you are fully informed by
>>>>the question, your answer should be to advice him to switch.
>>>
>>>Who is "you"? - The candidate was innocent. So how could he have a clue about
>>>the exact relations? That was my point. Only the psychological situation of the
>>>candidate mattered. Not the one of the host or ours or Marilyn's. Is this ok for
>>>you?
>>
>>Well I don't know about "psychological situation" part, but the information
>>regarding who knows what is important. The host must know, and the candidate
>>must know that the host knows.
>
>How could he?
>
>Please also read the following post:
>
>http://www.talkchess.com/forums/1/message.html?254195
>
>Already days ago I wrote it.
>
>Rolf Tueschen

Yes I know, their simulations make some assumptions which is the basis of (at
least some of) the disagreement.

But, to revert to a point about the doors, if you only have 1 chance on the
show, why then does it matter if the door open always or just in 1 single case?

The problem is there are several questions in the blend here, makes the whole
thing confusing.

I will just stick to the first question on the page you linked to, so for my
sake we can forget about the doors.

"Suppose you're on a game show, and you're given a choice of three doors. Behind
one door is a car; behind the others, goats. You pick a door-;say No. 1-;and the
host, who knows what's behind the doors, opens another door-;say No. 3-;which
has a goat. He then says to you, “Do you want to pick door No. 2?” Is it to your
advantage to switch your choice? "

So we agree that a contestant may or may not have the knowledge needed, but
eventhough it is the contestant that should decide in the actual show, it isn't
the contestant that should decide NOW, now it is YOU, and you have just been
fully informed.

I believe an equivalent (but much less confusing) formulation of the question
could be:

"Suppose George is on a game show, and George is given a choice of three doors.
Behind one door is a car; behind the others, goats. George picks a door, and the
host, who knows what's behind the doors, opens another door, which has a goat.
He then says to George, “Do you want to pick door No. 2?” Is it to George's
advantage to say yes? "

Obviously it isn't George he is asking, it is you who knows the truth.

So I believe Marilyn gave the correct answer/explanation after all.
The short answer would have been "yes".

-S.



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