How big a margin

[Lardonio]

Hi, I have a lot of historical data for all football betting markets, but the market I think is most fun to bet in is the correct scores market. But I'm wondering how big a margin I should calculate in order to be successful. I'm thinking - if my historical data says the odds of a 1-0 happening is 10% then of course the true odds is 10. If I can get 11 then that is a 10 percent margin, which is enough to keep most gamblers happy. But if I look at it another way it does not seem so tempting. If the true odds is 10, then again, the true chance of it happening is 10%. If the true odds is 11, then the true chance of it happening is (cirka) 9.09% There's only a (cirka) 0.91% difference in the two chances, and of course with any betting prediction data, historical data, etc. the error margin is probably bigger than 1%. This way of looking at it is more depressing the higher the odds became, for example the difference between a 40-odds and a 50-odds is, of course 10 in odds which seems a lot, but only 0.5% in chance, which is "nothing". The way the correct score markets is priced, even in betfair, I feel like I'm almost doomed using any statistical method, and I guess this applies to any betting market. I'd like your feedback on this. Is there really any point in developing betting methods based on statistics alone?

[Gingertipster]

Re: How big a margin The way I do my betting on horses is to make a 100% book, but I am not so good to be 100% accurate. I don't back anything that is (imo) only just value. It depends on how easy I think a race is to work out but normally: e.g. something I believe is a 20% chance (true 4/1) I don't back at 9/2 18.18%, but would at 5/1 16.67% (A 3.33% difference). A true 9/1 shot 10% I'd want 11/1 8.33% (just 1.67% difference). At 40/1 2.43% I'd only want 66/1 1.5% (just 0.94% difference). Sounds as if I am just missing a price out but it's a little bit more complicated. I believe the bigger the price the easier it is to evaluate. Also, bookmakers mark ups are less the bigger the price. The bookie might put a 2% or 3% (if it's unexposed) mark up on a 4/1 shot; but would not do so at 40/1, 0.5% or 1% most likely in a competitive market. If they added the same mark up for everything there'd be no 100/1 shots and bigger. So in turn, our margin for error can be less the bigger the price. What price you are willing to take should depend on how good you are at spotting value. Hope that helps Lardonio Mark