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Wolfgang October 27th, 2006 09:40 PM

What's a boy to do?
 
An interesting problem was recently brought to my attention.

Let us say that you and I are standing next to a table on which I have
placed three boards identical in every respect except that each has a
different number painted on it.....1, 2, and 3, respectively.

I say to you that if you turn your back I will place a five dollar bill
under one of the boards and a slip of paper that says "you lose" under each
of the others. You then turn back to face the table and point to or name
the board you think has the five dollar bill under it. If you're right, you
win the five bucks.

We proceed. You pick, say, board number one. I say, "O.k., tell you what,
I like you so I'm going to make this easier for you," and I remove board
number three to show you that it has a "you lose" tag under it. Obviously,
the five dollars must be under one of the other two. "So," I say, "would
you like to stick with your original pick, or change your mind?"

It is a given that the game is not rigged in any way and you are not being
fooled by anything ambiguous or otherwise misleading in the description.

The question.......what should you do?

Wolfgang




[email protected] October 27th, 2006 09:55 PM

What's a boy to do?
 

Wolfgang wrote:
An interesting problem was recently brought to my attention.

Let us say that you and I are standing next to a table on which I have
placed three boards identical in every respect except that each has a
different number painted on it.....1, 2, and 3, respectively.

I say to you that if you turn your back I will place a five dollar bill
under one of the boards and a slip of paper that says "you lose" under each
of the others. You then turn back to face the table and point to or name
the board you think has the five dollar bill under it. If you're right, you
win the five bucks.

We proceed. You pick, say, board number one. I say, "O.k., tell you what,
I like you so I'm going to make this easier for you," and I remove board
number three to show you that it has a "you lose" tag under it. Obviously,
the five dollars must be under one of the other two. "So," I say, "would
you like to stick with your original pick, or change your mind?"

It is a given that the game is not rigged in any way and you are not being
fooled by anything ambiguous or otherwise misleading in the description.

The question.......what should you do?


Assuming that I trust you, it doesn't matter. It's 50/50 chance
you can stick with your current pick or switch.

Given it's you, it REALLY doesn't matter since the $5 is probably
in your pocket.
- Ken


[email protected] October 27th, 2006 09:57 PM

What's a boy to do?
 

Wolfgang wrote:
An interesting problem was recently brought to my attention.

Let us say that you and I are standing next to a table on which I have
placed three boards identical in every respect except that each has a
different number painted on it.....1, 2, and 3, respectively.

I say to you that if you turn your back I will place a five dollar bill
under one of the boards and a slip of paper that says "you lose" under each
of the others. You then turn back to face the table and point to or name
the board you think has the five dollar bill under it. If you're right, you
win the five bucks.

We proceed. You pick, say, board number one. I say, "O.k., tell you what,
I like you so I'm going to make this easier for you," and I remove board
number three to show you that it has a "you lose" tag under it. Obviously,
the five dollars must be under one of the other two. "So," I say, "would
you like to stick with your original pick, or change your mind?"

It is a given that the game is not rigged in any way and you are not being
fooled by anything ambiguous or otherwise misleading in the description.

The question.......what should you do?


Assuming that I trust you, it doesn't matter. It's 50/50 chance
you can stick with your current pick or switch.

Given it's you, it REALLY doesn't matter since the $5 is probably
in your pocket.
- Ken


rb608 October 27th, 2006 09:58 PM

What's a boy to do?
 
Wolfgang wrote:
An interesting problem was recently brought to my attention.


Ah yes, the famous Monty Hall Puzzle. Go ahead & tell 'em the answer;
they won't believe it anyway. g

Joe F.


Wolfgang October 27th, 2006 10:03 PM

What's a boy to do?
 

"rb608" wrote in message
ups.com...
Wolfgang wrote:
An interesting problem was recently brought to my attention.


Ah yes, the famous Monty Hall Puzzle.


Spoilsport.

Go ahead & tell 'em the answer;
they won't believe it anyway. g


Don't have to. You just did. :)

Wolfgang



Scott Seidman October 27th, 2006 10:07 PM

What's a boy to do?
 
"Wolfgang" wrote in :


The question.......what should you do?

Wolfgang



If I recall correctly, you should change your mind. When you chose the
first, you had a 1/3 chance of being right, and nothing has changed that.
If you change your mind now, that gives you a 2/3 chance of being correct.
I'm pretty sure I'm dead wrong on that 2/3 number, though, but the chance
is more than 0.5. The key is that the removal process is not random.


--
Scott
Reverse name to reply

rb608 October 27th, 2006 10:11 PM

What's a boy to do?
 
Wolfgang wrote:
Don't have to. You just did. :)


Do not for a moment think that this entire body of flyfishermen & women
even approach the level of geekiness necessary to be familiar with the
MH puzzle and an extended discussion of the answer. Methinks anyone
who already did know of the puzzle recognized as I did; so I doubt I
spoiled it for anyone. But for those who would now go look it up by
name instead of figuring out the answer would probably fish pegged
beads anyway. :-)

Joe F.


October 27th, 2006 10:33 PM

What's a boy to do?
 

"Wolfgang" wrote in message
...
An interesting problem was recently brought to my attention.

Let us say that you and I are standing next to a table on which I have
placed three boards identical in every respect except that each has a
different number painted on it.....1, 2, and 3, respectively.

I say to you that if you turn your back I will place a five dollar bill
under one of the boards and a slip of paper that says "you lose" under
each of the others. You then turn back to face the table and point to or
name the board you think has the five dollar bill under it. If you're
right, you win the five bucks.

We proceed. You pick, say, board number one. I say, "O.k., tell you
what, I like you so I'm going to make this easier for you," and I remove
board number three to show you that it has a "you lose" tag under it.
Obviously, the five dollars must be under one of the other two. "So," I
say, "would you like to stick with your original pick, or change your
mind?"

It is a given that the game is not rigged in any way and you are not being
fooled by anything ambiguous or otherwise misleading in the description.

The question.......what should you do?

Wolfgang


I'd knock you in the head and take the money. If it wasnt under the
boards it would surely be in your pocket along with several other pieces
of folding money. Problem solved!
"a friend"




Bob Weinberger October 27th, 2006 10:40 PM

What's a boy to do?
 

"Wolfgang" wrote in message
...
An interesting problem was recently brought to my attention.

Let us say that you and I are standing next to a table on which I have
placed three boards identical in every respect except that each has a
different number painted on it.....1, 2, and 3, respectively.

I say to you that if you turn your back I will place a five dollar bill
under one of the boards and a slip of paper that says "you lose" under
each of the others. You then turn back to face the table and point to or
name the board you think has the five dollar bill under it. If you're
right, you win the five bucks.

We proceed. You pick, say, board number one. I say, "O.k., tell you
what, I like you so I'm going to make this easier for you," and I remove
board number three to show you that it has a "you lose" tag under it.
Obviously, the five dollars must be under one of the other two. "So," I
say, "would you like to stick with your original pick, or change your
mind?"

It is a given that the game is not rigged in any way and you are not being
fooled by anything ambiguous or otherwise misleading in the description.

The question.......what should you do?

Wolfgang


The obvious answer is to pick up board no.3, hit you over the head with it,
find the $5 ( plus any other spare change you have in your pocket) and
leave. 8~ ).

Bob Weinberger



Wolfgang October 27th, 2006 11:36 PM

What's a boy to do?
 

rb608 wrote:
Wolfgang wrote:
Don't have to. You just did. :)


Do not for a moment think that this entire body of flyfishermen & women
even approach the level of geekiness necessary to be familiar with the
MH puzzle and an extended discussion of the answer.


The thought never occurred to me. Trust me. :)

Methinks anyone
who already did know of the puzzle recognized as I did; so I doubt I
spoiled it for anyone. But for those who would now go look it up by
name instead of figuring out the answer would probably fish pegged
beads anyway. :-)


Precisely.......Google.

I bumped into this yesterday in a delightful little novel called "The
Curious Incident of the Dog In the Night-Time" by Mark Haddon. The
narrator, a 15 year old autistic boy named Christopher Boone, relates
his adventure as an amateur sleuth (ala his hero, Sherlock) and
runaway. He's something of a mathematical savant. As Haddon, through
Chrisopher, relates the story, the question was put to Marylin vos
Savant in "Parade" magazine by one Craig F. Whitaker of Columbia
Maryland. Wikipedia confirms this (while making it clear that this is
"a widely known statement" of the problem and thus, presumably, not the
first), so I assume that the quotes Haddon provides from responses to
Ms. Savant's answer, that you should always change your answer and pick
the final door, are also genuine:

"I'm very concerned with the general public's lack of mathematical
skills. Please help by confessing your error."--Robert Sachs, Ph.D.,
George Mason University

"There is enough mathematical illiteracy in this country, and we don't
need the world's highest IQ propagating more. Shame!"--Scott Smith,
Ph.D., University of Florida

"I am in shock that after being corrected by at least three
mathemeticians, you still do not see your mistake."--Kent Ford,
Dickinson State University

"I am sure you will receive many letters from high school and college
students. Perhaps you should keep a few addresses for help with future
columns."--W. Robert Smith, Ph.D., Georgia State University

"You are utterly incorrect...How many irate mathemeticians are needed
to get you to change your mind?"--E. Ray Bobo, Ph.D., Georgetown
University

"If all those Ph.D.'s were wrong, the country would be in very serious
trouble."--Everett Harman, Ph.D., U.S. Army Research Institute


I started this thread because it was a fascinating problem......not,
for me, so much because of the answer (which, naturally, I got wrong)
or because of the solutions (which I can sort of dimly
comprehend.....for about as long as I am looking at them), but because
it is such a truly beautiful illustration of the axiom that it ain't so
much what we don't know as what we know that ain't so that ****s us
up.....which is, in turn, a simply gorgeous paradox.

I posted the quotes included above because, of course, I knew that the
usual ****weasels would be incapable of resisting the temptation to
make asses of themselves yet again and thus append themselves to the
list. More of them would unquestionably have done so if you hadn't
netted kennie so quickly. :)

Wolfgang
"gravy" it's called......and i like it.


Wolfgang October 27th, 2006 11:40 PM

What's a boy to do?
 

Scott Seidman wrote:
"Wolfgang" wrote in :


The question.......what should you do?

Wolfgang



If I recall correctly, you should change your mind. When you chose the
first, you had a 1/3 chance of being right, and nothing has changed that.
If you change your mind now, that gives you a 2/3 chance of being correct.
I'm pretty sure I'm dead wrong on that 2/3 number, though, but the chance
is more than 0.5.


Actually, I believe your exactly right about the 2/3. :)

Um.....well, it's been a couple hours since I last looked at the
solution, so I could be wrong. :(

The key is that the removal process is not random.


Yep.

Wolfgang


Wolfgang October 27th, 2006 11:43 PM

What's a boy to do?
 

Bob Weinberger wrote:

The obvious answer is to pick up board no.3, hit you over the head with it,
find the $5 ( plus any other spare change you have in your pocket) and
leave. 8~ ).


Ladies and gentlemen, we have a winner! :)

Wolfgang
don't forget to torch the place on your way out.......dna is a stone
cold bitch!


Wolfgang October 27th, 2006 11:57 PM

What's a boy to do?
 

basilratbone wrote:

I'd knock you in the head and take the money. If it wasnt under the
boards it would surely be in your pocket along with several other pieces
of folding money. Problem solved!
"a friend"


Do I know you?

Um......aside from your profession, that is.

Dumbass.

Wolfgang


Wolfgang October 28th, 2006 02:56 AM

What's a boy to do?
 

wrote:
Wolfgang wrote:
An interesting problem was recently brought to my attention.

Let us say that you and I are standing next to a table on which I have
placed three boards identical in every respect except that each has a
different number painted on it.....1, 2, and 3, respectively.

I say to you that if you turn your back I will place a five dollar bill
under one of the boards and a slip of paper that says "you lose" under each
of the others. You then turn back to face the table and point to or name
the board you think has the five dollar bill under it. If you're right, you
win the five bucks.

We proceed. You pick, say, board number one. I say, "O.k., tell you what,
I like you so I'm going to make this easier for you," and I remove board
number three to show you that it has a "you lose" tag under it. Obviously,
the five dollars must be under one of the other two. "So," I say, "would
you like to stick with your original pick, or change your mind?"

It is a given that the game is not rigged in any way and you are not being
fooled by anything ambiguous or otherwise misleading in the description.

The question.......what should you do?


Assuming that I trust you, it doesn't matter. It's 50/50 chance
you can stick with your current pick or switch.

Given it's you, it REALLY doesn't matter since the $5 is probably
in your pocket.


Uh huh. Was there anything else?

Wolfgang


Tim J. October 28th, 2006 03:43 AM

What's a boy to do?
 

Wolfgang typed:
An interesting problem was recently brought to my attention.


I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room is now
quite crowded, we remove dead people, but add bad people. How many
people are now in the room?
--
TL,
Tim
---------------------------
http://css.sbcma.com/timj/



vincent p. norris October 28th, 2006 03:45 AM

What's a boy to do?
 
When you chose the first, you had a 1/3 chance of being right, and nothing has changed that.

Scott, I assume you know what a Tontine is. Suppose you and two
friends form one. Overlooking health and age differences and the fact
that one smokes and drinks heavily, each of you has one chance in
three of winning.

Later, one of the others dies. Now, what is your chance of winning?

vince

[email protected] October 28th, 2006 04:02 AM

What's a boy to do?
 
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.


I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room is now
quite crowded, we remove dead people, but add bad people. How many
people are now in the room?


That could be BAFfling...

TC,
R

Tim J. October 28th, 2006 04:39 AM

What's a boy to do?
 

typed:
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.


I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room is
now quite crowded, we remove dead people, but add bad people. How
many people are now in the room?


That could be BAFfling...


.... but wrong.
--
TL,
Tim
---------------------------
http://css.sbcma.com/timj/



[email protected] October 28th, 2006 04:46 AM

What's a boy to do?
 
On Fri, 27 Oct 2006 23:39:09 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.

I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room is
now quite crowded, we remove dead people, but add bad people. How
many people are now in the room?


That could be BAFfling...


... but wrong.


How?

deaf-dead = 2, 2 + bad = baf, no?

May not be, but if not, ???

TC,
R

Tim J. October 28th, 2006 05:24 AM

What's a boy to do?
 

typed:
On Fri, 27 Oct 2006 23:39:09 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.

I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room
is now quite crowded, we remove dead people, but add bad people.
How many people are now in the room?

That could be BAFfling...


... but wrong.


How?

deaf-dead = 2, 2 + bad = baf, no?

May not be, but if not, ???


You never left the room.
--
TL,
Tim
---------------------------
http://css.sbcma.com/timj/



[email protected] October 28th, 2006 05:58 AM

What's a boy to do?
 
On Sat, 28 Oct 2006 00:24:58 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 23:39:09 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.

I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room
is now quite crowded, we remove dead people, but add bad people.
How many people are now in the room?

That could be BAFfling...

... but wrong.


How?

deaf-dead = 2, 2 + bad = baf, no?

May not be, but if not, ???


You never left the room.


Um, you didn't say "we you in a room and _add_ deaf people..." Phrased
the way you originally phrased it, wouldn't I be including in "deaf
people?" I'm not a math geek, and I've never heard of this "oldie," I
just thought it was more of logic thing with hex - f to d and back to f,
but ??? I could understand it if it spelled something, but including me
makes it bb0, no? Is that something hilarious to math prof-types or
something?

TC,
R

Bob Weinberger October 28th, 2006 07:35 AM

What's a boy to do?
 

"Wolfgang" wrote in message
ups.com...
Actually, I believe your exactly right about the 2/3. :)

Um.....well, it's been a couple hours since I last looked at the
solution, so I could be wrong. :(

The key is that the removal process is not random.


Yep.

Wolfgang


Yes, the key from a pure mathematical probability standpoint is that the
removal process is not random. However, from a human nature standpoint the
fact that the removal is not random could also dictate in some circumstances
that I should not switch.
If the rules are that you must always reveal one of the losers, then the MH
problem solution dictates that it is in my interest to switch. However such
a rule was not stated in the question you posed. If I suspect that you are
aware that I most likely am familiar with the MH problem solution, and if I
also think that you think that I am unaware that you have that knowledge
then, if you reveal one of the losers, it is probably not in my interest to
switch (geez what a tortured sentence). Conversely, with those respective
mindsets, if you choose not to reveal one of the losers I probably should
switch. Of course after playing a few times in the absence of a rule to
always reveal one of the losers, the activity would quickly go to each of us
trying to second guess the other.

Bob Weinberger



Cyli October 28th, 2006 10:38 AM

What's a boy to do?
 
On Fri, 27 Oct 2006 22:45:54 -0400, vincent p. norris
wrote:

When you chose the first, you had a 1/3 chance of being right, and nothing has changed that.


Scott, I assume you know what a Tontine is. Suppose you and two
friends form one. Overlooking health and age differences and the fact
that one smokes and drinks heavily, each of you has one chance in
three of winning.

Later, one of the others dies. Now, what is your chance of winning?

vince



Depends somewhat on your and their morality. There's a reason
tontines were outlawed...

--
Antiquis temporibus, nati tibi similes in rupibus
ventosissimis exponebantur ad necem.

http://www.visi.com/~cyli

asadi October 28th, 2006 02:44 PM

What's a boy to do?
 

"Wolfgang" wrote in message
...
An interesting problem was recently brought to my attention.
The question.......what should you do?


Wolfgang




When you first picked, you had a one in three chance of being right.

With one board removed, your pick 'still' has a one in three (33 1/3 %)
chance of being right.

However, with only two boards left, you can chance your chances. If you pick
a different board (the remaining) you will now have a one in two (50%)
chance of being right. it behooves you to re-pick.

john



October 28th, 2006 08:35 PM

What's a boy to do?
 

wrote in message
...
On Sat, 28 Oct 2006 00:24:58 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 23:39:09 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.

I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room
is now quite crowded, we remove dead people, but add bad people.
How many people are now in the room?

That could be BAFfling...

... but wrong.

How?

deaf-dead = 2, 2 + bad = baf, no?

May not be, but if not, ???


You never left the room.


Um, you didn't say "we you in a room and _add_ deaf people..." Phrased
the way you originally phrased it, wouldn't I be including in "deaf
people?" I'm not a math geek, and I've never heard of this "oldie," I
just thought it was more of logic thing with hex - f to d and back to f,
but ??? I could understand it if it spelled something, but including me
makes it bb0, no? Is that something hilarious to math prof-types or
something?

TC,
R
I would still knock you in the head and take your money along with

the others. I would be the baddest person in the room. there would be a
lot of dead people in the room . All those who woud remove them would also
be dead. so , the answer is no one alive. I would leave with yours and
theirs money. problem solved




jeffc October 28th, 2006 10:37 PM

What's a boy to do?
 

"Wolfgang" wrote in message
...

The question.......what should you do?


The easiest way to convince yourself of the correct answer (since it's
non-intuitive) is to play the game with someone. After a short while,
you'll realize that the only way you can get it right if you don't switch is
if you picked it right from the beginning - in other words, 1 chance in 3.



Wolfgang October 29th, 2006 12:05 AM

What's a boy to do?
 

jeffc wrote:
"Wolfgang" wrote in message
...

The question.......what should you do?


The easiest way to convince yourself of the correct answer (since it's
non-intuitive) is to play the game with someone. After a short while,
you'll realize that the only way you can get it right if you don't switch is
if you picked it right from the beginning - in other words, 1 chance in 3.


Sure, first they take all yer shiny new nickels.......

Hey, I've only got just so many five dollar bills, ya know! :(

Anyway, that's right.....so long as we stress the "convince" part, as
opposed to learn. Unless and until you become familiar with the
correct solution to the Monty Hall problem (whether it's explained to
you or you work the logic out for yourself) intuition can lead you down
a long and, if it's presented as a betting game, ruinous road.

Wolfgang
who wouldn't bet any of his few remaining shiny new nickels on the
prospect of selling these revolutionary analyses to the folks who run
vegas. :)


vincent p. norris October 29th, 2006 01:55 AM

What's a boy to do?
 
When you chose the first, you had a 1/3 chance of being right, and nothing has changed that.

Scott, I assume you know what a Tontine is. Suppose you and two
friends form one. Overlooking health and age differences and the fact
that one smokes and drinks heavily, each of you has one chance in
three of winning.

Later, one of the others dies. Now, what is your chance of winning?

vince


Depends somewhat on your and their morality. There's a reason
tontines were outlawed...


Yeah, but I was presenting it as a question involving probabilities,
not morality. (Or did you accidently omit the "t" from "mortality"?

vince

vincent p. norris October 29th, 2006 01:00 AM

What's a boy to do?
 
When you first picked, you had a one in three chance of being right.

Right.

With one board removed, your pick 'still' has a one in three (33 1/3 %)
chance of being right.


John, care to respond to my question, posted above?

vince

riverman October 29th, 2006 03:02 AM

What's a boy to do?
 

"jeffc" wrote in message
.. .

"Wolfgang" wrote in message
...

The question.......what should you do?


The easiest way to convince yourself of the correct answer (since it's
non-intuitive) is to play the game with someone. After a short while,
you'll realize that the only way you can get it right if you don't switch
is if you picked it right from the beginning - in other words, 1 chance in
3.


Or just play by yourself:
http://math.ucsd.edu/~crypto/Monty/monty.html

This puzzle right smack dab in the center of my realm, as its a regular
component of one of my classes. I can take you all to school on the solution
on several levels, but I'm not working today so you're off the hook.

MEANWHILE: how about this cherry;

You toss three darts at a target. Dart A misses the target, then Dart B
misses by even more. What is the probability that Dart C will miss by more
than Dart A?

--riverman



Opus McDopus October 29th, 2006 04:27 AM

What's a boy to do?
 

"riverman" wrote in message ...

Or just play by yourself:
http://math.ucsd.edu/~crypto/Monty/monty.html
--riverman


I got it right, 3 out of 5 times, by changing my selection each timed.

Op



riverman October 29th, 2006 06:40 AM

What's a boy to do?
 

"Opus McDopus" wrote in message
...

"riverman" wrote in message
...

Or just play by yourself:
http://math.ucsd.edu/~crypto/Monty/monty.html
--riverman


I got it right, 3 out of 5 times, by changing my selection each timed.

Op


Yep. A better way to convince yourself that changing doors is the best
strategy is to make a spinner out of a paper clip and a piece of paper. Draw
a circle divided in thirds, and unbend the paper clip so it works as a
pointer, and hold it in the center with the pencil when you spin it. Agree
beforehand that the prize is in a given section, and decide that you will
always switch. After about three spins, it becomes abundantly obvious how it
all works.

--riverman



Cyli October 29th, 2006 11:32 AM

What's a boy to do?
 
On Sat, 28 Oct 2006 20:55:19 -0400, vincent p. norris
wrote:

When you chose the first, you had a 1/3 chance of being right, and nothing has changed that.

Scott, I assume you know what a Tontine is. Suppose you and two
friends form one. Overlooking health and age differences and the fact
that one smokes and drinks heavily, each of you has one chance in
three of winning.

Later, one of the others dies. Now, what is your chance of winning?

vince


Depends somewhat on your and their morality. There's a reason
tontines were outlawed...


Yeah, but I was presenting it as a question involving probabilities,
not morality. (Or did you accidently omit the "t" from "mortality"?

If one of the tontine has none of the former, the other is apt to
discover the quietness of the latter....

--
Antiquis temporibus, nati tibi similes in rupibus
ventosissimis exponebantur ad necem.

http://www.visi.com/~cyli

Cyli October 29th, 2006 12:31 PM

What's a boy to do?
 
On Sun, 29 Oct 2006 11:02:22 +0800, "riverman"
wrote:



Or just play by yourself:
http://math.ucsd.edu/~crypto/Monty/monty.html

This puzzle right smack dab in the center of my realm, as its a regular
component of one of my classes. I can take you all to school on the solution
on several levels, but I'm not working today so you're off the hook.

Unfortunately, the first 4 or 5 times I tried it with not changing, I
was right every time. Then the odds started to work out, but I had
those early successes to work out of my mind.

--
Antiquis temporibus, nati tibi similes in rupibus
ventosissimis exponebantur ad necem.

http://www.visi.com/~cyli

asadi October 29th, 2006 01:25 PM

What's a boy to do?
 

"vincent p. norris" wrote in message
...
When you chose the first, you had a 1/3 chance of being right, and
nothing has changed that.


Scott, I assume you know what a Tontine is. Suppose you and two
friends form one. Overlooking health and age differences and the fact
that one smokes and drinks heavily, each of you has one chance in
three of winning.

Later, one of the others dies. Now, what is your chance of winning?

vince


If I'm one of the remaining members I'd say your chances were pretty damned
good....

john



[email protected] October 29th, 2006 02:39 PM

What's a boy to do?
 
On Sat, 28 Oct 2006 06:35:31 GMT, "Bob Weinberger"
wrote:


"Wolfgang" wrote in message
oups.com...
Actually, I believe your exactly right about the 2/3. :)

Um.....well, it's been a couple hours since I last looked at the
solution, so I could be wrong. :(

The key is that the removal process is not random.


Yep.

Wolfgang


Yes, the key from a pure mathematical probability standpoint is that the
removal process is not random.


Not as I see. As I see it, those supporting 50-50 odds aren't looking
at the situation properly. I vaguely remembered the puzzle with Marilyn
vos Savant, and of the explanations I saw, none really phrased the
explanation both simply _and_ accurately (not that they aren't out
there, I just didn't see them). Here's my explanation:

Look at in reverse. Given the way Wolfgang phrased it, by switching,
you essentially get to pick two boards. Let's change the phrasing such
that if once you had picked board #1, he had given you the choice of
sticking to that choice (1 chance in 3) or switching to pick _both_ of
the two remaining boards (2 chances in 3), most people can easily see
the odds advantage of switching and as such, would switch to picking two
boards. You know one of the two will not and cannot have a five under
it.

At that point, Wolfgang turns one board of your two over and it's the
one that isn't the five. He now offers you the choice of switching back
to board #1. If you switch, you have traded your two-board pick back to
Wolfgang for your original one board (1 chance in 3) pick. The fact that
one board of your two-board (2 chances in 3) pick is now revealed is not
material to the odds. You knew and expected that one of the two boards
of your two-board choice couldn't and wouldn't have the five under it,
so why would the fact that things are as you expected and as they have
to be influence your new choice?

This explanation is for the puzzle as Wolfgang explained, not all
possible variants. For example, if a third person walks up at the point
after the first board is turned over and is offered a chance to get in
on things by picking one of the two remaining boards, their odds are
50-50, but they had different "rules" (this "each "hand's" _rules_ are
different" is why blackjack ain't a heads-up game). And secondly, if
you continue to play and Wolfgang is free to "change the rules" in every
"game," the proper choice could change depending on what he does or
doesn't do.

TC,
R

[email protected] October 29th, 2006 02:41 PM

What's a boy to do?
 
On 28 Oct 2006 14:35:06 -0500, basil ratbone wrote:


wrote in message
.. .
On Sat, 28 Oct 2006 00:24:58 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 23:39:09 -0400, "Tim J."
wrote:


typed:
On Fri, 27 Oct 2006 22:43:52 -0400, "Tim J."
wrote:


Wolfgang typed:
An interesting problem was recently brought to my attention.

I like that one. Here's another less thought provoking oldie:

We put you in a room and fill it with deaf people. Given the room
is now quite crowded, we remove dead people, but add bad people.
How many people are now in the room?

That could be BAFfling...

... but wrong.

How?

deaf-dead = 2, 2 + bad = baf, no?

May not be, but if not, ???

You never left the room.


Um, you didn't say "we you in a room and _add_ deaf people..." Phrased
the way you originally phrased it, wouldn't I be including in "deaf
people?" I'm not a math geek, and I've never heard of this "oldie," I
just thought it was more of logic thing with hex - f to d and back to f,
but ??? I could understand it if it spelled something, but including me
makes it bb0, no? Is that something hilarious to math prof-types or
something?

TC,
R
I would still knock you in the head and take your money along with

the others. I would be the baddest person in the room. there would be a
lot of dead people in the room . All those who woud remove them would also
be dead. so , the answer is no one alive. I would leave with yours and
theirs money. problem solved


BASIL?!...BASIL?!...BASIL?!....you sound like a flowery ****...

Opus McDopus October 29th, 2006 02:49 PM

What's a boy to do?
 

"asadi" wrote in message
...

If I'm one of the remaining members I'd say your chances were pretty
damned good....

john


Are we goin to remain on non-speaking terms forever?

Op



rb608 October 29th, 2006 03:55 PM

What's a boy to do?
 
wrote in message
Not as I see. As I see it, those supporting 50-50 odds aren't looking
at the situation properly.


For example, if a third person walks up at the point
after the first board is turned over and is offered a chance to get in
on things by picking one of the two remaining boards, their odds are
50-50, but they had different "rules" (this "each "hand's" _rules_ are
different" is why blackjack ain't a heads-up game).


As one who understands the mathematics, but still has difficulty
rationalizing the counter-intuitive nature of the answer, I think this
somewhat illuminates the crux. If the question is, "What is the probability
of selecting the correct answer from two remaining random choices?", the
answer is 1/2. That is the simplest and most understandable question.
Everybody gets it. But that's not the actual question posed by the problem,
nor are the choices random. The question posed is, "What is the probablity
of selecting the correct answer through this process?" The correct answer
to that is 2/3.

Joe F.



[email protected] October 29th, 2006 05:03 PM

What's a boy to do?
 
On Sun, 29 Oct 2006 15:55:00 GMT, "rb608"
wrote:

wrote in message
Not as I see. As I see it, those supporting 50-50 odds aren't looking
at the situation properly.


For example, if a third person walks up at the point
after the first board is turned over and is offered a chance to get in
on things by picking one of the two remaining boards, their odds are
50-50, but they had different "rules" (this "each "hand's" _rules_ are
different" is why blackjack ain't a heads-up game).


As one who understands the mathematics, but still has difficulty
rationalizing the counter-intuitive nature of the answer, I think this
somewhat illuminates the crux. If the question is, "What is the probability
of selecting the correct answer from two remaining random choices?", the
answer is 1/2. That is the simplest and most understandable question.
Everybody gets it. But that's not the actual question posed by the problem,
nor are the choices random. The question posed is, "What is the probablity
of selecting the correct answer through this process?" The correct answer
to that is 2/3.


I don't see how it's (objectively) counter-intuitive, and I think
attempting to get too involved in "math" (beyond the basic) makes it
more, rather than less difficult - for example, if it had been 4 boards,
two were turned over revealing losers, and then the choice to change
were given, to me, common sense indicates the odds say change your pick
because of the same reasons I feel it does with 3. If you must have
"math," I'm fairly sure the formula would be that the odds in favor of
switching are pretty close to if not exactly x-1/x and the odds in favor
of sticking are always exactly 1/x, when x is greater than 2, but I'm
not a mathematician, so ??? Perhaps the odds in favor need to account
for the first pick when x is higher than 3 - such that it isn't quite
x-1/x - but it's always going to be better odds than 1/x. ****, that's
confusing...that's why, IMO, algebra isn't the way to figure this out.

About the only thing I can figure is that it is much like many threads
on ROFF in that most folks, myself included at times, don't always
_read_ what they are "reading," but rather, um, infer from what is
written by what they _think_ is being said. In this case, they are
simply ignoring that there are 3, not 2, boards and therefore, the
chances cannot be 1 in 2.

Heck, given the "game" as outlined by Wolfgang, there's nothing
presented in the "rules" preventing the person from choosing the
revealed losing board - they were simply offered a chance to change
their pick. It would be the chooser making the obvious choice not to
choose it because they can clearly see they won't win (they don't need
to know that the chance of winning is 0 in 3).

TC,
R

Joe F.



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