Understanding American Odds
Odds-ratios are often used in analysis of clinical trials. While they have useful mathematical properties, they can produce counter- intuitive results: In some cases the log-odds are used, which is the logit of the probability.
Most simply, odds are frequently multiplied or divided, and log converts multiplication to addition and division to subtractions. The odds in favour of a blue marble are 2: One can equivalently say, that the odds are There are 2 out of 15 chances in favour of blue, 13 out of 15 against blue. That value may be regarded as the relative probability the event will happen, expressed as a fraction if it is less than 1 , or a multiple if it is equal to or greater than one of the likelihood that the event will not happen.
In the very first example at top, saying the odds of a Sunday are "one to six" or, less commonly, "one-sixth" means the probability of picking a Sunday randomly is one-sixth the probability of not picking a Sunday. While the mathematical probability of an event has a value in the range from zero to one, "the odds" in favor of that same event lie between zero and infinity. The odds against Sunday are 6: It is 6 times as likely that a random day is not a Sunday.
The use of odds in gambling facilitates betting on events where the relative probabilities of outcomes varied. For example, on a coin toss or a match race between two evenly matched horses, it is reasonable for two people to wager level stakes. However, in more variable situations, such as a multi-runner horse race or a football match between two unequally matched sides, betting "at odds" provides a perspective on the relative likelihoods of the possible outcomes.
In the modern era, most fixed odds betting takes place between a betting organisation, such as a bookmaker , and an individual, rather than between individuals. Different traditions have grown up in how to express odds to customers, older eras came with betting odds between people, today which is illegal in most countries, it was referred as "odding", an underground slang word with origins based in the Bronx. Favoured by bookmakers in the United Kingdom and Ireland , and also common in horse racing , fractional odds quote the net total that will be paid out to the bettor, should he or she win, relative to the stake.
However, not all fractional odds are traditionally read using the lowest common denominator. Fractional odds are also known as British odds, UK odds,  or, in that country, traditional odds. Odds with a denominator of 1 are often presented in listings as the numerator only. A variation of fractional odds is known as Hong Kong odds. Fractional and Hong Kong odds are actually exchangeable.
The only difference is that the UK odds are presented as a fractional notation e. Both exhibit the net return. The European odds also represent the potential winnings net returns , but in addition they factor in the stake e. Favoured in continental Europe , Australia , New Zealand and Canada , decimal odds quote the ratio of the payout amount, including the original stake, to the stake itself. This is considered to be ideal for parlay betting, because the odds to be paid out are simply the product of the odds for each outcome wagered on.
Decimal odds are also favoured by betting exchanges because they are the easiest to work with for trading, as they reflect the inverse of the probability of an outcome. Decimal odds are also known as European odds , digital odds or continental odds. Moneyline odds are favoured by American bookmakers. The figure quoted is either positive or negative. Moneyline odds are often referred to as American odds.
A "moneyline" wager refers to odds on the straight-up outcome of a game with no consideration to a point spread. In most cases, the favorite will have negative moneyline odds less payoff for a safer bet and the underdog will have positive moneyline odds more payoff for a risky bet.
However, if the teams are evenly matched, both teams can have a negative line at the same time e. The book price is effectively a measure of the competitiveness of the odds prices on offer. In gambling, the odds on display do not represent the true chances as imagined by the bookmaker that the event will or will not occur, but are the amount that the bookmaker will pay out on a winning bet, together with the required stake.
In formulating the odds to display the bookmaker will have included a profit margin which effectively means that the payout to a successful bettor is less than that represented by the true chance of the event occurring. This profit is known as the 'over-round' on the 'book' the 'book' refers to the old-fashioned ledger in which wagers were recorded, and is the derivation of the term 'bookmaker' and relates to the sum of the 'odds' in the following way:.
The true odds against winning for each of the three horses are , and respectively. This represents the odds against each, which are , and , in order. This value of 30 represents the amount of profit for the bookmaker if he gets bets in good proportions on each of the horses. And the expected value of his profit is positive even if everybody bets on the same horse.
The art of bookmaking is in setting the odds low enough so as to have a positive expected value of profit while keeping the odds high enough to attract customers, and at the same time attracting enough bets for each outcome to reduce his risk exposure. A study on soccer betting found that the probability for the home team to win was generally about 3.
It was about 3. Making a profit in gambling involves predicting the relationship of the true probabilities to the payout odds. Sports information services are often used by professional and semi-professional sports bettors to help achieve this goal.
The odds or amounts the bookmaker will pay are determined by the total amount that has been bet on all of the possible events. They reflect the balance of wagers on either side of the event, and include the deduction of a bookmaker's brokerage fee "vig" or vigorish.
From Wikipedia, the free encyclopedia. This article is about the gambling and statistical term. For the alternative rock band, see Odds band. For playing chess with odds, i. For the documentary film, see The Odds Against. This article may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts , without removing the technical details. March Learn how and when to remove this template message.
This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. May Learn how and when to remove this template message. Journal of Statistics Education. Retrieved 11 July Archived from the original on Jul 14, Retrieved 1 May The Science of Conjecture: Evidence and Probability Before Pascal.
The Johns Hopkins University Press. Retrieved 16 May Bayesian Data Analysis 2nd ed. Retrieved 27 March Archived from the original on Retrieved 10 December Expected Values and variance in bookmaker payouts: A Theoretical Approach towards setting limits on odds. Journal of Prediction Markets. Retrieved 22 August Explicit use of et al. Retrieved from " https: Someone who accepts bets and sets odds.
Placing bets on the team with the high odds, and the low odds, to minimize loss. On any event, the current odds or point spreads on the game. The money you pay, or risk, on an outcome or event.
Know that odds at the track tell you amount of profit you will make per dollar spent. To determine profit, multiply the amount you bet by the fraction. Understand that fractions greater than one mean a team is an underdog.
This makes sense, because you would expect a bet on the underdog to have a higher payout. If you have a hard time with fractions, then see if there is a larger number on top then on bottom. When you bet for the underdog, it is called betting "against the odds. Know that moneyline bets only concern what team will win the game. Odds are presented as a positive or negative number next to the team's name.
A negative number means the team is favored to win, while a positive number indicates that they are the underdog. This means the Cowboys are the favorites, but pay out less money if a bet on them wins. Try out an online to check your math when you first get started. Soon enough it will be second nature, but for now ask a friend or search for a calculator that fits your betting needs.
You also get the money you bet back. To calculate how much profit you make per dollar spent, divide the amount you are going to spend by Multiply this number by the moneyline to see your potential profit.
When betting on the favorite, you take less risk, and thus earn less. Like positive odds, you earn back your bet when winning. To calculate profit, divide by the moneyline to find out the profit made per dollar spent. Notice that point spreads adjust the score for the favorite team. This is easiest to see with an example: If the New York Knicks are playing the Boston Celtics, and Boston is favored to win by a 4-point spread, then a bet on Boston only pays out if Boston wins by more than 4 points.
A bet on New York pays out if New York wins or if they lose by less than 4 points. If the favorite wins by the spread exactly, it is called a "push" and all bets are refunded. In the example, if Boston wins , then it is a push and no one collects a profit. If you see "half-odds" a 4. Ask your bookie about the "vig," which determines your potential profit. Also known as the "juice," the vigorish is the commission charged for placing a bet.
Typically the vig is , and you read this number like a moneyline bet see above. Sometimes there are different vigs for each team. A line from before might look like this: If the score is exactly what the bookies set, then the bet is a push and everyone gets their money back. Make sure to check this with your bookie first, however.
Not Helpful 9 Helpful The should read Not Helpful 6 Helpful The "" means that a football team is favored to win by 13 points. For you to win the bet, the team must win by more than 13 points.
Not Helpful 0 Helpful 4. Not Helpful 18 Helpful Not Helpful 7 Helpful When I see a whole number alone on an odds sheet, what does it mean? Multiplying your stake by decimal odds gives your total return, not your profit which is total return -stake. To get to fractional from decimal, add 1. Not Helpful 29 Helpful What does odds of 9 to 4 mean on a baseball team to win the World Series?
Not Helpful 0 Helpful 1. Not Helpful 7 Helpful 3. Not Helpful 35 Helpful 5. Not Helpful 50 Helpful 3.