This is the minimum sample size you need in the absence group to estimate the true population odds ratio with the required relative precision and confidence level. This is what you expect the odds ratio to be, i.e., the odds of the outcome given presence of the property you are looking for an association with relative to the same outcome in the absence of that property. Note that the actual precision achieved after you collect your data will be more or less than this target amount, because it will be based on the odds ratio and prevalence observed in the data and not the expected values supplied to the calculator. The relative precision is the percentage by which the lower limit for your confidence interval is less than the estimated odds ratio. Try changing the five inputs (the relative precision, confidence level, absence case prevalence, expected odds ratio and presence to absence ratio) to see how they affect the sample size. If we would like to estimate the odds ratio with 95% confidence and a relative precision of 50%, how many samples are required?
Decimals
The larger the sample size, the more certain you can be that the estimates reflect the population, so the narrower the confidence interval. Multiply this number by the ratio of presences to absences that you plan to sample to calculate the sample size for the presence group. Otherwise this is the ratio of the number of presences compared to the number of absences that you plan to sample. This is the proportion of absence cases (for the property you are looking for an association with) that you expect to have the outcome. Trusted by independent bookmakers and punters to work out returns, you can be sure that the calculations are accurate. What is a lucky 15 bet?
🏈 American Football / 🏏 Cricket / 🏀 Basketball
So a $100 bet at American odds of +270, would see you win $270 in profit (plus you’d bet your $100 back too for a total return of $370). You can see the bracket parts (£200) refers to the profit you make on the bet, whereas the non-bracket part of the equation simply returns your betting stake to you (£50) This is the case for every fractional odds calculation but it gets more complicated when the unit stake is not one (such as when it is 13/8 or similar). As odds are displaying the implied probability of a particular event occurring, there is an equivalence between the three. So, odds tell you how much chance there is of one of the possible outcomes happening based on implied probability.
In football betting, 21/10 odds show up quite frequently—especially in markets where form, momentum, or tactical matchups play a crucial role. Odds of 21/10 typically appear in betting markets where the outcome is far from certain—but still very possible. That means if your bet wins, you multiply your stake by 3.10 to get your total return. They are all telling you that this is a bet with a potential profit of £2.10 for every £1 staked, so just slightly higher than a 2/1 bet. If you’ve ever browsed a bookmaker’s site or looked at a betting slip and seen odds of 21/10, you might have scratched your head wondering what that actually means.
How to use the Bet Calculator
If you want success as a bettor, recording details of your bets is absolutely essential. If you ask any professional punter for their most important betting tip, many of them will tell you the same thing. So, if your analysis tells you that Manchester City have a better than 71.4 percent chance of winning, you might be considering making a odds to percentage bet. Those odds expressed as a percentage are 71.4, which means Manchester City are being quoted as a 71.4 percent chance to win the game.
- Each format presents odds in a distinct manner, catering to the preferences of bettors in different regions.
- Some calculators may even offer options to convert into less commonly used formats.
- Every set of odds reflects an implied probability – in other words, what the bookmaker thinks are the chances of that outcome happening.
- Free bets expire after 30 days.