Odds vs Chances/Probability

[PairTheBoard]

If you have 1 chance in 10 of winning or 10% probability, the "odds" are 9-1 against you.

That's how we use the term "odds" around here - and that's how it's taught in school. However, I'm wondering if this use of the term "odds" is universal. Do they use it differently in gambling circles in England? While looking up the Kelly Criteria on Google I ran across these two sites.

Punting Ace Kelly Site

Betting Systems Kelly Site

They both use the term "odds" in the Kelly formula to be 10 in the example above. They have "odds -1" in the denominator. Not a good thing for coin flips unless they mean for the "odds" term to be 2 in that case.

I think the sites are British because they use the terms Punter and Punting.

Anybody know what the Brits are up to with this?

PairTheBoard

[punter11235]

I cant answer your question but I found this part interesting :

[ QUOTE ]
That's how we use the term "odds" around here - and that's how it's taught in school.

[/ QUOTE ]

In Poland the concept of "odds" is not taught in school. Almost nobody use it in real life too. Its always 25% or 1/4 chance. Never 3-1 odds.

[KJ o]

The same goes for Sweden. I still struggle with the odds thing. Chances are always a percentage, and betting is always in terms of return, i.e. a single number stating how many times your bet you receive if you win. For instance, the odds of 1.73 would mean that a bet of SEK 100 would give you SEK 173 in your hand if you won.

Spreads, wig, rake or whatever the house takes out is always hidden, so you always see what you get net of that.

[lastcardcharlie]

Same in UK. We don't teach odds, just probabilities. At least, odds isn't on the Curriculum. But then again neither is basic set theory (unions, intersections, subsets, ..) in all of eleven years (5 - 16) of being taught mathematics. Also, those not considered clever enough are put in for an exam which they can't possibly pass even if they get 100%. etc.

[AaronBrown]

There's no difference internationally, although people often misuse the terms.

Bets can be stated as X for Y or X to Y. 2 for 1 means get $2 for each $1 bet, that is the other party takes your $1 and keeps it, and pays you $2 if you win. It's how casinos think about odds. This is fair if the chance of winning is 1/2.

2 to 1 means you get $2 if you win and pay $1 if you lose, which is fair if your chance of winning is 1/3. This is how two bettors will think of a bet.

The second one is the correct use of the word "odds" in stating bets. In terms of probabilities, the odds of an event is the probability of it happening divided by the probability of it not happening. So the odds of flipping heads with a fair coin is 0.5/0.5 = 1.

Odds = Probability / (1 - Probabilitiy) to 1
Probability = Odds / (1 + Odds)

But if someone says the odds of that occurring are 10%, you know they mean "probability" instead of odds. If they say the probability is 2 to 1, they should mean odds, but it's anybody's guess what they actually mean.

[jason1990]

[ QUOTE ]
Bets can be stated as X for Y or X to Y.

[/ QUOTE ]
I had never seen this "X for Y" terminology until a couple of years ago when I visited a particular casino and looked at their craps table. All of their payouts were listed as "X for Y". I didn't even notice the little word "for". I just saw the two numbers, X and Y, and interpreted this as "X to Y". Consequently, it appeared to me that many of the center bets on the table has no house edge at all! This was inconceivable to me, so I asked the pit boss about it. Surprisingly, it took several minutes to get the issue cleared up. In the end, I didn't get a clear explanation from the pit boss, but simply had to figure it out on my own from clues in the conversation. This terminology may be common, but I still think it's a bit of a "cheap trick". [img]/images/graemlins/smile.gif[/img]

[BobJoeJim]

[ QUOTE ]
If you have 1 chance in 10 of winning or 10% probability, the "odds" are 9-1 against you.

That's how we use the term "odds" around here - and that's how it's taught in school. However, I'm wondering if this use of the term "odds" is universal. Do they use it differently in gambling circles in England? While looking up the Kelly Criteria on Google I ran across these two sites.

Punting Ace Kelly Site

Betting Systems Kelly Site

They both use the term "odds" in the Kelly formula to be 10 in the example above. They have "odds -1" in the denominator. Not a good thing for coin flips unless they mean for the "odds" term to be 2 in that case.

I think the sites are British because they use the terms Punter and Punting.

Anybody know what the Brits are up to with this?

PairTheBoard

[/ QUOTE ]
In this particular case, they are using "odds" to refer to the betting odds offered, given in the decimal system.

A break even bet would have decimal odds of 2.00, since you get back twice what you put in. This is the equivalent to +100 in the American system. 3.00 is the same as +200, 1.50 is the same as -200, etcetera.