You are using an old web browser. Such browsers do not support modern web technologies and do not offer proper security. Please update your browser or download one of the others suggested for free.
Mozilla Firefox |
Google Chrome |
Internet Explorer |
You can't "predict" when betting. You calculate possibilities, compare them to the odds offered by the bookmaker, and look for an edge. If there is no edge, you just skip the game. Often, there will be tens or even hundreds of games offered but you'll only be able to find 1 or 2 with good enough value to bet them. You need good discipline to bet only those games and skip the rest, instead of trying to "predict" what will happen. If you don't have this discipline, the bookmaker's juice will break you sooner or later.
In my opinion, there are 2 things we always need to remember before betting:
1) Discipline - always bet when you have an edge, never chase losses;
2) Bankroll management - I'd use Kelly criterion for 2-way bets (most US sports, over/under in all sports), flat for 3-way and speculative (high volatility like parlays and exact scores in soccer).
2-way bets are bets with 2 possible outcomes, like flipping a coin (sides when there are no draws, over/unders). In US sports, most betting is 2-way. Bets that are not 2-way are for example sides with draws (e.g. soccer), horse races, also parlays and teasers (even if they consist only of 2-way events) etc.
With 2-way bets, it's easier to determine a sustainable edge/winning chance than with other bets, that's why it's OK to use Kelly to calculate the optimal size of your bets.
Great stuff endy - thanks for posting....for myself and a lot of folks the Kelly criterion doesn't work very well becuase the trick is quantifying the edge...for those of us unsure of that I recommend flat betting no more than 1-2% of your bankroll on any one game...if you bet more than that without being able to quantify your edge then you are falling into the "predicting" trap that you mentioned....
You're absolutely right, finance: the trick is quantifying the edge - after making sure that you have any edge at all, of course :). There are too many random factors in any given game so it's not an exact science but if you have enough history data from previous bets, you can calculate it closely enough for practical purposes.
Here's how Kelly works for me (simplified explanation):
Let's say that I have a history of betting "over 3.5" in soccer (3+ years at various odds from about +100 to +170, 20+ games per week) which shows that I have 10% ROI in the long run. I want to bet a game that offers me odds of +120. I calculate my chance of winning the bet (based on the odds and my long term ROI) at exactly 50% or 0.5 (betting 1 unit, 50% of the time I win 1.2 units and 50% of the time I lose 1 unit which is exactly 0.1 units profit or 10% ROI). The formula for the bet amount is:
f = (p * (b+1) - 1)/b
f - percentage of bankroll to bet
p - probability of winning
b - winnings if 1 unit is bet
so in the example case p = 0.5, b = 1.2 and f calculates to 0.083 which means that I should bet 8.3% of my bankroll on the game for optimal results.
If the game offers me odds of +160 instead of +120, then my probability of winning (to keep the same long term ROI) is 42.3% so using Kelly I should only bet 6.24% of my bankroll. Which makes perfect sense as +160 compared to +120 leads to higher variation even if the long term ROI is the same.
But if this week I decide to bet on the Tigers in Game 3 of the World Series for example, I won't use Kelly because I have no history at all betting on baseball. So I can't calculate any edge, and I most likely don't even have an edge at all (and should expect to lose about 5% in the long term just like any other random bettor). I would only use Kelly for my "over 3.5" bets in the leagues that I've played the past 3 years.