Odds

Q: What are odds?

A: Odds are the price that a betting market assigns to a match result. For a bettor, odds determine the payout after a winning ticket. For quant research, odds also imply the market's view of the probability of that result.

Q: What is the relationship between odds and probability?

A: In decimal odds, the rough implied probability is the reciprocal of the odds. For example, odds of 2.00 imply about 50%. In real markets, the bookmaker margin and payout ratio must be considered, so the implied probabilities across all outcomes usually add up to more than 100%.

Q: Why are odds the core variable in football quant research?

A: The key question is not only who is likely to win. The key question is whether the price is worth buying. A team may have a high win probability, but if the odds are too low, the bet may have no value. Conversely, a lower-probability outcome may have positive expectation if the odds are high enough.

Q: What is special about odds in China Sports Lottery football betting?

A: In China Sports Lottery football betting, the ticket odds are usually fixed once the ticket is printed. The prize is paid according to the ticket. This makes the buy-in price clear and gives backtesting a cleaner way to define the strategy's historical return condition.

Q: How do odds affect staking?

A: Odds directly affect expected value and staking fraction. If the researcher's true probability estimate is higher than the probability implied by the odds, a probability edge may exist. The Kelly formula can then be used to calculate a theoretical staking fraction.

Q: How do bookmakers calculate odds?

A: For a traditional bookmaker, odds are both a probability expression and a tool for guiding betting flow. Imagine a coin-toss game with two possible outcomes. In theory, heads and tails each have a 50% probability over a large number of trials. If the bookmaker wants a 5% margin and two users each stake 50 yuan, the bookmaker receives 100 yuan, keeps 5 yuan, and pays 95 yuan to the winner. Since the winning user staked 50 yuan and receives 95 yuan, the decimal odds are 1.90. The bookmaker earns its margin regardless of which side wins.

Football moneyline odds are built on a similar idea. Asian handicap, over/under, total goals, and correct score markets follow related logic, although the calculation details differ.

Q: Where do odds sit in this site's knowledge graph?

A: Odds are the middle layer connecting market, probability, strategy, and bankroll management. They connect upward to China Sports Lottery, sideways to quantitative strategy and backtesting, and downward to Kelly sizing, expected value calculation, and Python implementations.