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Monty Hall Spinoff Thread: St. Petersburg Paradox

Posted on 8/12/17 at 4:40 pm
Posted by STLDawg
The Lou
Member since Apr 2015
3718 posts
Posted on 8/12/17 at 4:40 pm
Let's say you have the opportunity to play a coin flip game. If you get heads, you win $1. If you get two heads in a row, you get $2. To generalize, for however many heads in a row you get, the amount you win doubles with each head. If you get a tails at any time, the game ends and you get the amount of money you won so far.

The issue comes when deciding what is a fair price to play such a game. You have a 1/2 chance of winning $1, a 1/4 chance of $2, a 1/8 chance of $4, and so on. As the chance of continuing the game decreases at the same rate the amount of winnings increases, the expected value of such a game is infinite.

How much would you pay to play?
This post was edited on 8/12/17 at 4:43 pm
Posted by High C
viewing the fall....
Member since Nov 2012
53815 posts
Posted on 8/12/17 at 4:43 pm to
You said spinoff.
Posted by Kafka
I am the moral conscience of TD
Member since Jul 2007
142023 posts
Posted on 8/12/17 at 4:44 pm to
quote:

Monte Carlo
hosted Let'sa maka deala

Posted by rmnldr
Member since Oct 2013
38231 posts
Posted on 8/12/17 at 4:45 pm to
quote:

How much would you pay to play?


about tree fiddy
Posted by deeprig9
Unincorporated Ozora, Georgia
Member since Sep 2012
64051 posts
Posted on 8/12/17 at 4:46 pm to
50 cents
Posted by upgrayedd
Lifting at Tobin's house
Member since Mar 2013
134865 posts
Posted on 8/12/17 at 4:47 pm to
Col. Mustard in the study with the wrench.
This post was edited on 8/12/17 at 4:48 pm
Posted by KosmoCramer
Member since Dec 2007
76526 posts
Posted on 8/12/17 at 4:48 pm to
Expected Value
Posted by Nado Jenkins83
Land of the Free
Member since Nov 2012
59672 posts
Posted on 8/12/17 at 4:49 pm to
More like a flipoff.
Posted by SlowFlowPro
Simple Solutions to Complex Probs
Member since Jan 2004
422585 posts
Posted on 8/12/17 at 4:58 pm to
quote:

Expected Value

infinity
Posted by Dr RC
The Money Pit
Member since Aug 2011
58082 posts
Posted on 8/12/17 at 5:00 pm to
42
Posted by WG_Dawg
Hoover
Member since Jun 2004
86500 posts
Posted on 8/12/17 at 5:25 pm to
Idk, probably like a dollar.

It doesn't matter if you flip 10000 heads in a row, the chance of the next flip is still 50/50. Odds are you wouldn't win more than a few bucks so I certainly wouldn't put much into it.
Posted by East Coast Band
Member since Nov 2010
62798 posts
Posted on 8/12/17 at 5:36 pm to
Whatever the calculated average winnings are, Vegas would set the entry to be much higher than that.
Say, your average payout is $5 in this game. Vegas would probably charge $8 to play.

$3 average profit for every time played.Vegas wins again and builds another billion dollar casino, using 0 tax dollars.
Posted by Gray Tiger
Prairieville, LA
Member since Jan 2004
36512 posts
Posted on 8/12/17 at 5:46 pm to
quote:

You have a 1/2 chance of winning $1, a 1/4 chance of $2, a 1/8 chance of $4, and so on.


That isn't right. Each flip of the coin is 50/50. The coin has no memory nor control over the flip.
quote:

As the chance of continuing the game decreases at the same rate the amount of winnings increases, the expected value of such a game is infinite.



No it is the same odds for every flip.
Posted by KosmoCramer
Member since Dec 2007
76526 posts
Posted on 8/12/17 at 5:49 pm to
quote:

No it is the same odds for every flip


So by the odds of flipping tails once, and flipping it 100 times in a row is the exact same.

Got it.

Posted by fightin tigers
Downtown Prairieville
Member since Mar 2008
73681 posts
Posted on 8/12/17 at 5:50 pm to
Probably a couple hundred dollars
Posted by Nado Jenkins83
Land of the Free
Member since Nov 2012
59672 posts
Posted on 8/12/17 at 5:55 pm to
Actually depends on the coin. Heads is heavier than tails in the case of a quarter
Posted by Martini
Near Athens
Member since Mar 2005
48853 posts
Posted on 8/12/17 at 5:59 pm to
quote:



Monte Carlo

hosted Let'sa maka deala


I did upvote
Posted by tom
Baton Rouge
Member since Jun 2007
8158 posts
Posted on 8/12/17 at 5:59 pm to
quote:

The issue comes when deciding what is a fair price to play such a game. You have a 1/2 chance of winning $1, a 1/4 chance of $2, a 1/8 chance of $4, and so on.

Nope.
Posted by mdomingue
Lafayette, LA
Member since Nov 2010
30343 posts
Posted on 8/12/17 at 6:13 pm to
I think he's saying the odds for each individual flip are 50/50.

The probability that you do it 100 times in a row are 1 in 1,267,650,600,228,229,401,496,703,205,376.

I feel pretty confident on this as I recall reading this from Marilyn vos Savant years ago but my track record today has not been great, as you can testify.
Posted by KosmoCramer
Member since Dec 2007
76526 posts
Posted on 8/12/17 at 6:19 pm to
This poster said in regards this previous post:

quote:

quote:

You have a 1/2 chance of winning $1, a 1/4 chance of $2, a 1/8 chance of $4, and so on.



That isn't right. Each flip of the coin is 50/50. The coin has no memory nor control over the flip.


That's wrong. Each flip is 50/50 but the series of events isn't. The poster above is confused.
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