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 07-27-2008, 05:26 AM   #1
journeyman
 
Join Date: Jan 2007
Location: defending blinds with vigour
Posts: 232
does 4:1 odds mean you have 25% or 20% chance to win??

also whats your formula to work out your percentage to win with 3/2 odds etc.

i know its a noob question buy hey, im a noob to maths

cheers
coatsie is offline   Reply With Quote
Old 07-27-2008, 05:51 AM   #2
Carpal \'Tunnel
 
BruceZ's Avatar
 
Join Date: Sep 2002
Posts: 11,570
Re: does 4:1 odds mean you have 25% or 20% chance to win??

4:1 against = 1/(4+1) = 20%.

This is 1 win for every 4 losses, or 1 win for every 4+1 = 5 plays.

Quote:
Originally Posted by coatsie View Post
also whats your formula to work out your percentage to win with 3/2 odds etc.
3:2 against = 2/(3+2) = 40%. (2 wins for every 3+2 = 5 plays).

3:2 in favor = 3/(3+2) = 60%. (3 wins for every 3+2 = 5 plays).

Last edited by BruceZ; 07-27-2008 at 05:56 AM.
BruceZ is offline   Reply With Quote
Old 07-27-2008, 11:20 AM   #3
Pooh-Bah
 
AaronBrown's Avatar
 
Join Date: May 2005
Location: New York
Posts: 4,119
Re: does 4:1 odds mean you have 25% or 20% chance to win??

There are two confusing things here.

Probability is usually stated as the number of equally likely ways something can happen versus the total number of ways. So I say you have 5 chances in 36 of rolling an 8 with two dice, because there are 5 ways to make an 8 (62, 53, 44, 35 and 26) out of 36 possible rolls.

Payouts are usually stated as the amount you win versus the amount you put up, so 4 to 1 means one side puts up $1 and the other side puts up $4. In this case, fair odds for rolling an 8 is 31:5 (which in turn is conventionally reduced to 6.2:1 because people don't like numbers higher than 20 unless the other side is 1). However, sometimes payouts are stated as 4 for 1, meaning you pay $1 which you don't get back, and either win $4 or nothing.

If the odds are 4 to 1 (also written 4:1), then you need a 20% probability of winning, 1 / (4 + 1), to make it a fair bet. If the wager is stated as 4 for 1, you need a 25% chance, 1 / 4, to make it fair.

Gamblers tend to think in terms of symmetrical bets, so 4 to 1. Casinos and mathematicians, for different reasons, tend to think in terms of one side paying money for the possible delivery of a payout.

So make sure you know if you're talking about payouts or probabilities and whether the ratio is stated as "to" or "for".
AaronBrown 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 12:48 PM.


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