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Subject: 
Re: math question (or pattern... whatever...)
Newsgroups: 
lugnet.off-topic.geek
Date: 
Tue, 4 Mar 2003 20:03:23 GMT
Viewed: 
375 times
  
In lugnet.off-topic.geek, David Eaton writes:
In lugnet.off-topic.geek, Bruce Schlickbernd writes:
I think your analysis is incorrect, precisely because you did *not* list all
outcomes.

Choose  Prize  Door Revealed   Possible choices
1       1        2           Stay (win). Switch (lose).
1       1        3           Stay (win). Switch (lose).
1       2        3           Stay (lose).  Switch (win).
1       3        2           Stay (lose).  Switch (win).

Choose  Prize  Door Revealed   Possible choices
2       2        1           Stay (win). Switch (lose).
2       2        3           Stay (win). Switch (lose).
2       1        3           Stay (lose).  Switch (win).
2       3        1           Stay (lose).  Switch (win).

Choose  Prize  Door Revealed   Possible choices
3       3        1           Stay (win). Switch (lose).
3       3        2           Stay (win). Switch (lose).
3       1        2           Stay (lose).  Switch (win).
3       2        1           Stay (lose).  Switch (win).

12 different door combinations with 24 outcomes: 12 win if you stay, 12 win
if you switch.  The nine you list is very incomplete.

Actually, I explained (albeit briefly) why this isn't correct.

You see, you now have 2 listings for "Choose 1, Prize 1", "Coose 2, Prize
2", and "Choose 3, Prize 3", when each deserves *equal* probability to each
other possibility, like "Choose 2, Prize 3"-- which in your list, only gets
one entry. Basically, if you want to count "Choose 1, Prize 1, Door Revealed
2" and "Choose 1, Prize 1, Door Revealed 3" as *different*, then you have to
count each *other* selection twice as well, resulting in:


That doesn't make sense at all--

If I choose door 1 and the prize is behind door 1, the host can choose to
show me door 2 *or* door 3 - 2 possibilities

If I choose door one and the prize is behind door 2, the host can *only*
show me door 3 - one possibility

If I choose door one and the prize is behind door 3, the host can *only*
show me door 2 - one possibility

So if I choose door 1, there are only 4 possibilities, not 6, as you listed
below.

Now whether I switch or stay, as listed above, is 50/50

Dave K
-who is just getting more and more confus-ed by the second, but loving the
problem....

<snip>

DaveE



Message has 1 Reply:
  Re: math question (or pattern... whatever...)
 
(...) Doh. This is just coming back to haunt me. I should never have included the "door revealed" column. It's entirely irrelevant, and is only serving to confuse. A better list: Prize Choice Switch or Stay? 1 1 stay! 1 2 switch! 1 3 switch! 2 1 (...) (22 years ago, 4-Mar-03, to lugnet.off-topic.geek)

Message is in Reply To:
  Re: math question (or pattern... whatever...)
 
(...) Actually, I explained (albeit briefly) why this isn't correct. You see, you now have 2 listings for "Choose 1, Prize 1", "Coose 2, Prize 2", and "Choose 3, Prize 3", when each deserves *equal* probability to each other possibility, like (...) (22 years ago, 4-Mar-03, to lugnet.off-topic.geek)

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