Two Plus Two Publishing LLC Two Plus Two Publishing LLC
 

Go Back   Two Plus Two Poker Forums > General Gambling > Probability

Notices

Probability Discussions of probability theory

Reply
 
Thread Tools Display Modes
Old 07-28-2012, 02:05 PM   #1
stranger
 
Join Date: Jul 2012
Posts: 1
Heart bet with boyfriend

hey guys,
i am opening this thread because of a very important bet i have just made with my very smart boyfriend, because he didnt believe me the following theory about roulette:

I read in my psychology studies that when you bet on the SAME color each time you will lose less money on the long run than if you would switch it up (as in following your "gut feeling").




Karen
mysmartgirlfriend is offline   Reply With Quote
Old 07-28-2012, 02:50 PM   #2
Carpal \'Tunnel
 
Sherman's Avatar
 
Join Date: Jun 2005
Location: Psychology Department
Posts: 7,693
Re: bet with boyfriend

Hi Karen,

Either your psychology instructor sucks at probability or your misunderstood him/her. The expected value of betting red or black on a single spin in roulette is the same no matter what you bet (assuming the wheel is truly random). Your boyfriend wins this bet.

However, your idea is not totally off base. If someone tells you that in 100 games, team A will win 70 times and team B will win 30 times and you have no other information about those games, you are better off just betting on team A every time. Many people intuitively try to "probability match" by betting on A 70 times and B 30 times. While this is the only strategy for getting all 100 games perfectly right, on average it will do worse than simply betting on team A every time (in which you are guaranteed to be right 70 times and wrong 30 times).

Last edited by BruceZ; 07-30-2012 at 12:09 AM. Reason: 70 --> 30
Sherman is offline   Reply With Quote
Old 07-28-2012, 02:54 PM   #3
Carpal \'Tunnel
 
mburke05's Avatar
 
Join Date: Mar 2008
Location: Ruling with an iron pocketbook.
Posts: 11,503
Re: bet with boyfriend

http://en.wikipedia.org/wiki/Indepen...bility_theory)

Last edited by BruceZ; 07-28-2012 at 07:51 PM. Reason: Removed joke potentially offensive to new poster.
mburke05 is offline   Reply With Quote
Old 07-28-2012, 05:11 PM   #4
I need a hug
 
Join Date: Jan 2011
Location: Where you live
Posts: 4,111
Re: bet with boyfriend

+1

That's like saying it's more profitable to choose heads 100 times in a row when having a coin flip marathon. It's not.

Last edited by BruceZ; 07-28-2012 at 07:41 PM.
TensRUs is offline   Reply With Quote
Old 07-28-2012, 05:27 PM   #5
 
Join Date: Dec 2006
Posts: 6,190
Re: bet with boyfriend

Perhaps people bet less on average when they do not bounce between different bets based on their gut (chasing losses less for instance). That would explain why they lose less - it would be a function of how much a person bets, so the psychology aspect could be along those lines much like how when casinos started showing the past numbers the revenue went up because people bet based on patterns.

The OP left out human behavioral tendencies as part of the equation (ie: whether it is part or not).
Monteroy is offline   Reply With Quote
Old 07-28-2012, 05:29 PM   #6
Carpal \'Tunnel
 
BruceZ's Avatar
 
Join Date: Sep 2002
Posts: 10,946
Re: bet with boyfriend

Quote:
Originally Posted by Sherman View Post
If someone tells you that in 100 games, team A will win 70 times and team B will win 70 times
Bet with him.


Quote:
and you have no other information about those games, you are better off just betting on team A every time.
Unless you're making all 100 bets in advance, you'd do better by betting on B sometimes. For example, I'd always get the last game right, and that means that there is a 30% chance that I'll be betting on B in the last game (assuming 70/30).

But in Roulette where the spins are independent, and the probability of red and black are equal, it makes no difference which you bet on. Your probability of winning or losing any given amount after any given number of spins will be exactly the same, and on average you will lose 5.26% of the total money that you bet if it's a 00 wheel.
BruceZ is offline   Reply With Quote
Old 07-28-2012, 07:07 PM   #7
Carpal \'Tunnel
 
Sherman's Avatar
 
Join Date: Jun 2005
Location: Psychology Department
Posts: 7,693
Re: bet with boyfriend

Quote:
Originally Posted by BruceZ View Post
Unless you're making all 100 bets in advance, you'd do better by betting on B sometimes. For example, I'd always get the last game right, and that means that there is a 30% chance that I'll be betting on B in the last game (assuming 70/30).
Yes Bruce, I was presuming that you had to lay all 100 bets in advance.

To use a poker related situation, consider playing against a particular player who makes a particular bet with no more bets possible (either all in or on the last round of betting). You know that he would only do this as a bluff (30%) or with the nuts (70%). You are getting the right price to call because he does it as a bluff often enough. How often should you call? Of course the answer if every time you are in this situation. You should not try to guess which situations are the bluffs and which situations are the nuts. Obviously if you have some sort of tell that let's you know otherwise, you can do better than a pure "always call" strategy, but in the absence of such extra information always calling does better than trying to guess which times are bluffs and which times are not.
Sherman is offline   Reply With Quote
Old 07-28-2012, 07:25 PM   #8
veteran
 
Join Date: Mar 2009
Location: In the wires
Posts: 3,238
Re: bet with boyfriend

Quote:
Originally Posted by mysmartgirlfriend View Post
I read in my psychology studies that when you bet on the SAME color each time you will lose less money on the long run than if you would switch it up (as in following your "gut feeling").
Please describe where you read this, and if it's really in some kind of published scholarly material you should complain loudly to the idiots who wrote this.
NewOldGuy is offline   Reply With Quote
Old 07-28-2012, 08:15 PM   #9
 
Join Date: Dec 2006
Posts: 6,190
Re: bet with boyfriend

Likely the material had nothing to do with the odds of the game but rather the conditions in which people tend to bet larger amounts. Casinos always try to make their games more amenable to average bettors betting more, so I suspect this is tied more into that.
Monteroy is offline   Reply With Quote
Old 07-28-2012, 09:21 PM   #10
Pooh-Bah
 
SheetWise's Avatar
 
Join Date: Jul 2005
Location: Phoenix
Posts: 4,677
Re: bet with boyfriend

Was there anything in the article about "PSI missing"?
SheetWise is offline   Reply With Quote
Old 07-29-2012, 12:22 AM   #11
stranger
 
Join Date: Jun 2010
Posts: 2
Re: bet with boyfriend

obv is es latte. jedes mal is es wieder neue 50%. spielt 0 rolle was du wann nimmst. es muß jedes mal random sein!
weil das universim des letzten males existiert nicht mehr. es ist jedes mal (ein) "neues" universum/neue odds. history hat nur im metagame relvanz
stochastisch gesehen gibt es keine History.
Nur zwischen und für die/denen die sich an das alte uuniversum erinnern
gibt es history, aber das universum/unsere dimension hat doch kein gedächtnis;
und es hat doch immer noch infinite zeit um wieder breakeven zu kommen...

can somebody proof it, somehow?
dejan25 is offline   Reply With Quote
Old 07-29-2012, 03:11 AM   #12
veteran
 
Join Date: Mar 2009
Location: In the wires
Posts: 3,238
Re: bet with boyfriend

Quote:
Originally Posted by dejan25 View Post
can somebody proof it, somehow?
By definition, random events in the past can't affect future random events. Otherwise they would not be random.

Put another way, every spin of the roulette wheel is the first spin.
NewOldGuy is offline   Reply With Quote
Old 07-29-2012, 11:37 PM   #13
banned
 
omnimirage the II's Avatar
 
Join Date: Apr 2012
Location: madnak's biggest fan
Posts: 304
Re: bet with boyfriend

Quote:
Originally Posted by Sherman View Post
However, your idea is not totally off base. If someone tells you that in 100 games, team A will win 70 times and team B will win 70 times and you have no other information about those games, you are better off just betting on team A every time. Many people intuitively try to "probability match" by betting on A 70 times and B 30 times. While this is the only strategy for getting all 100 games perfectly right, on average it will do worse than simply betting on team A every time (in which you are guaranteed to be right 70 times and wrong 30 times).
I don't understand why D:
omnimirage the II is offline   Reply With Quote
Old 07-29-2012, 11:53 PM   #14
Carpal \'Tunnel
 
BruceZ's Avatar
 
Join Date: Sep 2002
Posts: 10,946
Re: bet with boyfriend

Quote:
Originally Posted by omnimirage the II View Post
I don't understand why D:
Team A wins 70 and team B wins 30. If you bet team A every time, you win 70 times. If you bet Team A 70 times and team B 30 times, on average you win 70% of the 70 games that you bet A, and 30% of the 30 games that you bet B, for an average of 0.7*70 + 0.3*30 = 58 games.
BruceZ is offline   Reply With Quote
Old 07-29-2012, 11:56 PM   #15
banned
 
omnimirage the II's Avatar
 
Join Date: Apr 2012
Location: madnak's biggest fan
Posts: 304
Re: bet with boyfriend

oh, I totally misread that. Wait people actually bet 70 times on A and 30 times on B in that scenario?
omnimirage the II is offline   Reply With Quote

Reply
      

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 12:57 AM.


Powered by vBulletin®
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.6.0 ©2011, Crawlability, Inc.
Copyright © 2008-2010, Two Plus Two Interactive