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Author Topic:   Three Curtains
PaulK
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Message 18 of 48 (729308)
06-08-2014 2:57 PM
Reply to: Message 12 by Capt Stormfield
06-08-2014 1:54 PM


Re: Probability Changes Based on Data
Yes, the strategy followed by the host matters.
In the standard problem it is assumed that the host ALWAYS reveals one of the prizes, and never reveals the car. In that case the solution is as has been stated.
Observing the show is the only way to work out if there is a strategy, and what it might be.

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 Message 12 by Capt Stormfield, posted 06-08-2014 1:54 PM Capt Stormfield has not replied

  
PaulK
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Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 23 of 48 (729314)
06-08-2014 3:47 PM
Reply to: Message 22 by NoNukes
06-08-2014 3:37 PM


Re: Press Your Luck
For analysing the problem, I'd say that the more interesting questions are
"is the car ever revealed?"
and
"what relationship, if any, is there between the choice to reveal and the contestant choosing correctly"
If the presenter has a strategy, it can be exploited.

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Replies to this message:
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PaulK
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Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 26 of 48 (729317)
06-08-2014 4:08 PM
Reply to: Message 24 by rstrats
06-08-2014 4:01 PM


Re: Three Curtains
Curtains or doors, goats or nothing - those are details which don't change the mathematics of the problem, and looking at the general problem will help understand this one.
If this is a one-time occurrence then we do need to know if the host is required to offer the choice to switch, and if not what criteria he uses to decide to offer the choice or not. Without that the problem is not solvable.

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Replies to this message:
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PaulK
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Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 28 of 48 (729319)
06-08-2014 4:34 PM
Reply to: Message 27 by rstrats
06-08-2014 4:29 PM


Re: Three Curtains
Then the question is unanswerable. Switching could be advantageous, it could be disadvantageous, There is no way to tell.

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PaulK
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Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 30 of 48 (729322)
06-09-2014 1:35 AM
Reply to: Message 29 by Modulous
06-08-2014 8:59 PM


Re: exploiting strategies
I was speaking loosely, but this is a rather different game. Switching has to be better or worse or the same as not switching. If it's the same (worst case for the contestant) then it's still a 50-50 guess. And even that's better than the 1/3 odds before revealing.

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Replies to this message:
 Message 31 by rstrats, posted 06-09-2014 6:50 AM PaulK has replied
 Message 34 by Modulous, posted 06-09-2014 8:36 AM PaulK has replied

  
PaulK
Member
Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 32 of 48 (729324)
06-09-2014 7:13 AM
Reply to: Message 31 by rstrats
06-09-2014 6:50 AM


Re: exploiting strategies
That's just another variation that makes no difference.

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PaulK
Member
Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 35 of 48 (729330)
06-09-2014 8:45 AM
Reply to: Message 34 by Modulous
06-09-2014 8:36 AM


Re: exploiting strategies
quote:
Actually depending on the strategy in play, switching can be worse than 50/50 for the contestant.
That's what I said. And that is why I've been saying that you need to know the strategy.
Simply by choosing when to offer the chance to switch the host can trivially guarantee that a switch will always win or always lose.

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 Message 34 by Modulous, posted 06-09-2014 8:36 AM Modulous has replied

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PaulK
Member
Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 36 of 48 (729331)
06-09-2014 8:48 AM
Reply to: Message 33 by rstrats
06-09-2014 8:30 AM


Re: exploiting strategies
Oh dear. The point is that offering the chance to choose the other two is no different from revealing one of the other two as losing and offering the chance to switch to the remaining one. So it doesn't change the analysis at all.

This message is a reply to:
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Replies to this message:
 Message 37 by rstrats, posted 06-09-2014 9:02 AM PaulK has replied

  
PaulK
Member
Posts: 17827
Joined: 01-10-2003
Member Rating: 2.3


Message 38 of 48 (729335)
06-09-2014 9:18 AM
Reply to: Message 37 by rstrats
06-09-2014 9:02 AM


Re: exploiting strategies
No, it depends on the host's strategy as I keep telling you.

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