General Betting
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On fotball matches you can bet on "clean sheet" for both teams. Feks "Arsenal clean sheet?"
When handicapping these bets I often find value betting on clean sheet for the favourite team, but not the underdog.
Most bettors seem to overestimate the possibillity of the underdog to score (at least one goal). But they don't seem to overestimate (or underestimate) the posibillity of the favourite to score at least one goal.
This surprises me a bit. I thought non professional bettors mostly overestimated the favourite, not the underdog.
I've just started betting on clean sheet so I don't know if my strategi will be profitable.
Any comments?
When handicapping these bets I often find value betting on clean sheet for the favourite team, but not the underdog.
Most bettors seem to overestimate the possibillity of the underdog to score (at least one goal). But they don't seem to overestimate (or underestimate) the posibillity of the favourite to score at least one goal.
This surprises me a bit. I thought non professional bettors mostly overestimated the favourite, not the underdog.
I've just started betting on clean sheet so I don't know if my strategi will be profitable.
Any comments?
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On the other side, overestimating the posibillity of the underdog to score at least one goal is not the same as overestimating the posibillity of the underdog to win the game.
But why don't bettors overestimate the posibillity of the favourite to score? Maybe the odds is to low? I'm fully aware that I may be doing something totally wrong when handicapping these lines (even though it does not sound like it).. |
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Let's take an example.
I assume the game will produce a total of 2,7 goals. I also conclude that 65 % of the goals will be scored by the home team (and 35 % by the away team). This means that the home team is expected to produce 1,75 goals and the away team 0,95 goals. Let's assume I'm right about this. From this it's fairly easy to find that the probability of the home team to score at least one goal is 83 % and the probabilit of the away team to score at least one goal is 58 %. From this I also know that the probability of "clean sheet" for the home team is 42 % and the probability of "clean sheet" for the away team is 17 %. The thing is that I very often find value betting on clean sheet for the favourite team (in this case the home team), but not the underdog. But let's assume I'm still right about the game producing 2,70 goals, but wrong about the other percentages. Let's assume that 60 % of the goals will be scored by the home team (and 40 % by the away team). This changes a lot. Now the probability of "clean sheet" for the home team is 34 % and the probability of "clean sheet" for the away team is 20 %. Now there’s no value in betting on clean sheet for the favourite team. But instead there’s value betting on the underdog! When one of the teams is a clear favourite there seems to great value in betting on clean sheet on one of the teams, no mather what precentages I use. If I do what I think is correct the value is on betting on clean sheet for the favourite. How could this be? If I'm doing this completely wrong why do my lines on clean sheet for the underdog always seem to agree fairly well with the lines on Betfair? To me this is a clear indication that I must be doing something right. |
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From this it's fairly easy to find that the probability of the home team to score at least one goal is 83 % and the probabilit of the away team to score at least one goal is 58 %.
How are you working that out? |
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Using the poisson distribution, the same way I use it when I conclude that if the game will produce a total of 2,7 goals there is a 49 % chance of the game to produce under 2,5 goals and a 6,8 % chance of the game to produce no goals (less than 0,5 goals).
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One more thing. When I handicap these Clean sheet lines in an "open" game, with no obious favourite, my lines agree with the market. But once there is a rather clear favourite I find value betting on clean sheet for the favourite. The bigger favourite the more value I find.
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Ok, I get slightly different values using poisson: 82.62% and 61.32%.
Can you give an example of a market for the games tomorrow where you think there might be value? |
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I checked my numbers once more, and youre right. I also get around 83 % and 61 %.
I can give you a market for this night where I think there's value. The brazilian fotball match: Flamengo - Vitoria. Starting 2330 (Norwegian time). I (and the market) assume the game will produce around 2,45 goals. I assume Flamengo will score around 65 % of the goals and Vitoria 35 %. From that I find (using poisson props) that there's a 57 % chance that Vitoria will score at least one goal, and therefore a 43 % chance of clean sheet for flamengo (meaning Vitoria will not score). From this the correct odds on "yes" on Clean sheet Flemango should be 2,33. And 1,75 on "no". Right now you can lay "no" at 1,63. The odds on "clean sheet" Vitoria is "correct" using the same procedure. Now I've probably told far too much. I hope I'm doing somethin wrong. If not everybody knows what to do :) |
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Clean Sheet Yes should be 2.64 imo
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which makes no 1.61
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Why should it be 2,64 and 1,61?
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I don't deny it though. I just ask.
It should be added that I've so far lost a lot of money betting on clean sheets. But I've just started, and everything can happen in the short run.. |
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well i didn't use poisson i just used the market as the price is already set in other places
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Well, don't we all know what the market says? The question is whether or not the market is right?
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What did you use specifically rocket?
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Investor have you checked my example above (flamengo - vitoria)? Do you follow my calculations. What I haven't told is how I conclude that Flamengo will score around 65 % of the goals and Vitoria 35 %. That I will not tell. But actually it does not matter here. The thing is that I get "correct" odds on one of the clean sheet bets but not on the other. If I adjust the percentages (65 and 35 %) I still will find "value" on one or both bets.
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Are you using the correct score market at all?
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What do you mean?
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I think the point being made is that the clean sheet price is coherent with the correct score market, and that the discrepancy you find would be apparent there too (ie its not specific to clean sheet prices)
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I guess you mean the price on score 0-0 in the correct score market. Yes I agree that the price on clean sheet should be coherent with tthat price. But it's not. I check it. In fact, if I use the price on score 0-0 insted of the price on under 2,5 goals to decide the probabillity of goals being scored I tend to find even more value on clean sheet bets. Contrary to what I expected.
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I think the answer to this lies in the nature of football itself and away from the odds/stats. If a strong favourite beats an inferior team well you usually find that a consolation goal is scored.
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Not just 0-0.
Add up the probability of 0-0, 1-0, 2-0 and 3-0 and you get a price for the home team to keep a clean sheet. How you deal with 4-0,5-0,6-0 is up to you. |
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The more I look into this the sure I am that I'm doing this correctly and that the market is wrong. At the same time it's realy hard to believe that the market can be that wrong. I'm really trying to be objective here. I don't wanna di this wrong and lose a lot of money. I don't have a big ego. I will admit it immediately if I'm wrong on this.
But here are some facts: In a match with no clear favourite I get odds that agree with the market odds, for both teams when betting on clean sheet. When there's a favourite my odds agree with the market when betting on clean sheet for the underdog, but I find value betting on clean sheet for the favourite. The market seem to overestimate the probability of the underdog to score. If a change the way I handicap the games, for example by adjusting the estimated total score up or down, or adjusting the percentage of the total goals scored by each team, the value betting on clean sheet for the favourite may disappear. But then I instead find value betting on clean sheet for the underdog. |
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My 'guess' would be that you're wrong, as Poisson doesn't seem to get 0-0, 1-0, 0-1 quite right.
Another way you can check it, is by cross referencing the clean sheet odds with the both teams to score market. If you multiply the probabilties of each team No clean sheet, it should lead to both teams to score. If your derived odds give a result that doesn't converge with this, it means that this market would be wrong also. You could then check this against correct score. If every market is in line, it either means the whole market is just wrong (possible but unlikely), or you are missing something. I would use the same method as rocket. If there is a [team] total goals market with decent liquidity, you can add 4+ goals to get a more complete picture. This will affect the odds much more for the favourite than a longshot of course, that's why I originally asked if you used the Correct Score market. |
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I've tried cross referenced the clean sheet odds with the both teams to score market. I use the same calculations to bet on both these markets. I often find value betting on both teams to score. But this market seems to be far more correct than the clean sheet market.
Regarding poisson. I don't agree that poisson is not good enough here. The reason is as following: In his book "The definitive guide to betting on fotball, Kevin Pullein has found, using data from 14 permier league seasons, the relationship between the average number of goals scored by a team in a game and the percentages og games in which team scored spesific numbers of goals, including no goals. His findings are very much in accordance with the numbers I get, using poisson. BUT, i agree with you. It has to be very unlikely that the market is totally wrong. I really try to find out what mistake I might be doing. So far with no results. |
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There are two posibillities here.
1. The market is wrong. 2. Poisson does not work well enough when the expected number of goals is low, AND the market (if using poisson) knows that. As I've said earlier. When there's a favourite my odds agree with the market when betting on clean sheet for the underdog, but I find value betting on clean sheet for the favourite. The market seem to overestimate the probability of the underdog to score. This might be because the underdog often is expected to score less than one goal. And here is where the poisson might fail. Poisson underestimate the probability of a goal when the expected score of a team is low, and the lower the expected score is, the more poisson underestimate this probability. I've noticed the same when a game is at it's last minutes. There often seem to be value betting on under towards the end of a match when using poisson. But is this because poisson fails on low numbers, underestimating the probability of a goal? Anybody who knows if this is the case? Is this a problem with poisson? Is it useless when the goal expectation is low (lower than 1 goal)? |
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I've noticed the same when a game is at it's last minutes. There often seem to be value betting on under towards the end of a match when using poisson. But is this because poisson fails on low numbers, underestimating the probability of a goal?
Poisson is useless towards the end of a game, unless you adjust the expected goals in the formula to compensate for the fact that more goals tend to be scored in this period than any other equivalent period of the game. Of course you have to take time added on by the officials into account as well. |
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I should add that any general model will become less accurate towards the end of a game, as what is going on on the field of play can dramatically affect the probabilities of outcomes.
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"Poisson is useless towards the end of a game", and you can forget the rest of the sentence. I've found that rather than trying to make it work, it's better to start from scratch and attempt to model it without poisson.
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Concidering the fact that it is very unlikely that the market is that wrong, and the fact that this strategi so far has not been profitable, I think I'll stick to what I know works.
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Re the ''clean sheet'' betting,
I have been betting occasionally on these markets, backing and laying both the favourite and outsider when appropriate. I have been quite successful, 10 wins from 17 bets so far since Aug 07., I only bet when the market is at least 20% below or above my price, which isn't too often. I calculate my prices using goal expectancy and goal superiority. |
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10 wins from 17 bets. But have you made a profit so far? It all depends on the odds. I don't count wins and losses. I count profit.
Anyway. 17 bets want tell you anything statistically. ANYTHING can happen after only 17 bets. That does not mean that you're not doing things right. But the fact that you've won 10 out of 17 bets does not tell you anything. I've made around 250 bets so far. I've lost more than I've won. But even 250 bets is far from enough to conclude. I quit not because I've lost money. I quit because at the moment I'm not confident enough that I'm doing this correctly. |
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10 wins from 17 bets. But have you made a profit so far? (yes I have, otherwise what would be the point of my post ?) It all depends on the odds. I don't count wins and losses. I count profit.
Anyway. 17 bets want tell you anything statistically. (No, but over 14 years of the Premier League does) ANYTHING can happen after only 17 bets. That does not mean that you're not doing things right. (Thank you) But the fact that you've won 10 out of 17 bets does not tell you anything. (It tells me that I am doing things right) I've made around 250 bets so far. (Over how long ?, I don't find that many qualifiers, and 250 wouldtake me about 2 years, besides Pullein has done the research for you, see page 50 of his book)) I've lost more than I've won. But even 250 bets is far from enough to conclude. I quit not because I've lost money. I quit because at the moment I'm not confident enough that I'm doing this correctly. (Perhaps your research on this type of bet was flawed) GL. |
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In fact I also use some of Pulleins research when handicapping these lines.
I've made 250 bets over a period of around 3 months. There are at least 300 in-play fotball matches each week where you can bet on clean sheet for both teams on each match. That means 600 possible bets every week. 3 months equals around 13 weeks. Wich again means nearly 8000 possible bets. So 250 is not that much. Over a period of two years there should be around 62.000 bets to handicap. If you handicap everyone (which of course is not realistic!) and only find value in 250, you only find value in around one in every 250 bet. Not much. Not worth it! The fact that you've won 10 in 17 does not tell you that you're doing things right. You admit it yourself that 17 bets want tell you anything statistically. Maybe something else is telling you that you're doing things right. But NOT the staistics - the fact that you've made a profit after 17 bets. |
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You can bet blindly on whatever you want to bet on (even on a casino) and make a profit after 17 bets. It's not that unlikely that it couls happen with a little luck (you don't need that much luck either). But that does not tell you that you're doing things right. If you're betting blindly you couldn't possibly be doing things right, when the odds is against you.
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livebetter, I don't bet on just ''clean sheets'', this season so far I have bet
on 'clean sheets'(17) 'correct scores' (1) 'match odds' (22) 'corner odds' (14) overs/unders'(9) 'first corner' (5) 'total corners' (5) 'Both to score' (5) 'Total goals' (1) 'Corner spreads' (4) 83 markets in total, 50 profitable, 29 unprofitable, with 3 break evens., overall nicely in profit. I only look mainly at tv matches and that keeps me nicely part time occupied. I've been in the betting game a long time so I would politely thank you not to patronise me with references to betting in casinos etc. My suggestion to you would be to specialise a bit more instead of covering so many foreign matches as you must be doing when you refer to 300 in play matches per week. I repeat, if you are behind after 250 bets then your betting is flawed somewhere along the way.GL in what you do, but don't rely on it (luck that is) |
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How can you be so sure that my betting i flawed because I'm behind after 250 bets? You don't know how much I'm behind. What if I'm just slightly behind, close to break even? 250 bets is not that much. I've earlier experienced to be way ahead after more than 700 bets, and then after 500 more bets (a total of 1200 bets)lost all the profit I had after 700 bets. That was possible even though I did exactly the same all along.
250 bets is normally far from enough to conclude. But of course it all depends on how much you've lost or won. If you've lost or won just a little you need far more bets to conlude, compared to having won or lost huge amounts. |
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I quit not because I've lost money. I quit because at the moment I'm not confident enough that I'm doing this correctly.
Your words. Does that not mean what you are doing is/was flawed ? |
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No. It means that I don't know whether or not it's flawed. If I was more sure on what I'm doing I would probably keep on even though I've lose money so far. But the fact that I've lost so far makes it more probable that what I'm doing is flawed, compared to having been in profit. But it does not prove anything.
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ok
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