Soccer Half Time / Full Time odds relationship with HT and FT result?

[gereqi]

Hi folks, I have been searching a lot over Google and into this forum, but haven't got a clear explanation and maybe a formula of HT/FT odds if they have any relationship at HT and FT. I have been reading through www.betgps.com and http://forum.punterslounge.com/threads/108005-Half-time-Full-time-odds?highlight=half+time+full+time etc etc. but was able just to get a partial idea... Maybe you can explain me a little bit better why for example, in the tomorrow's match the odds are like this at HT/FT: Arsenal FC - West Ham United FT Home (1): 1.4 (probability 0.71) Draw (X): 4.6 (probability 0.22) Away (2): 6.75 (probability 0.15) HT Home (1): 1.85 (probability 0.54) Draw (X): 2.45 (probability 0.41) Away (2): 6.25 (probability 0.16) HT/FT: 1/1 : 2.05 X/1 : 4.05 2/1 : 22.00 1/X : 17.50 X/X : 7.75 2/X : 19.50 1/2 : 50.00 X/2 : 15.00 2/2 : 13.00 I have been trying to reproduce the formula given:

Quoting user JENSPM ... The chance of a win is, 1-(A+(B*C)) Where: A = the chance of Marseille winning or grabbing a draw at HT B = the chance of Chelsea winning at HT C = the chance of Chelsea losing the match IF they are winning at HT the correct odds would then be 1/(1-(A+(B*C))) ...

but I should be getting them wrong because I can not reproduce not even closer any of the odd types of HT/FT like 1/1 or X/1 etc. Maybe someone can help me and give me a hint or a lead?

[Paparazzo]

Re: Soccer Half Time / Full Time odds relationship with HT and FT result? I guess that in the formula you should add a higher juice to the HT/FT market. Going back to your example your odds are at a 108% on 1x2, so firstly you have to normalize the percentages are (note this calculation might not 100% correct!, ie. longshot bias), Then you should know what is the probability that given the result of the FT given the HT results (ie. if HT is 1 80% of the times there will be a 1 at FT). Then you can use the Bayes theorem to derive the probabilities of HT/FT to calculate the true odds and see how much is the margin. But at the end you'll see what I stated (higher juice is involved). In your example the juice of HT/FT grows up to a 118%! This is because it is considered as an "exotic" market or simply is considered as an acca. I hope it helps...

[gereqi]

Re: Soccer Half Time / Full Time odds relationship with HT and FT result? Thanks for your reply Paparazzo, I understand that the bookies add the extra juice for their own profit, but in my tried formulas (one of which I have shown as example) it's closer than others, but still a lot different product from the bookies offer, even when I take in account the extra part of bookie... This challenge is driving me crazy as I was hoping to get it right in my mind and have it clearer

[froment]

Re: Soccer Half Time / Full Time odds relationship with HT and FT result? I don’t think you can calculate HT/FT odds based on these two datasets. They basically represent two different markets evaluated before kick-off, while HT/FT odds need to consider how the match will develop depending on a half-time result. Paparazzo has just explained it, but let me try to develop it further; in your example, home team was evaluated before kick off to have 54% chance to win half time, and 71% chance to win full time. Though, that chance to win full time largely depends on actual outcome of first half –Paparazzo said that chances of home team to win FT will be 80% if they win half time; however, that may be generally true, while in this specific example, when home team is clear favourite, I’d say that probability is even higher – if they were estimated at 71% before kick-off, it surely must rise to more than 80% if they win half time; I estimate that if home team is priced 1.40, and they lead by 1 goal at half-time, those odds would be around 1.15 - 1.20; if they lead by 2 goals, odds would be somewhere around 1.08, and so on. I will take 87% for this example, which corresponds to odds of 1.15. Hence, probability of HT/FT is not (probability of HT) * (probability of FT) as you calculated, but (probability of HT) * (probability of FT given corresponding outcome of HT) Let me try to do an example; I will use very rough odds estimation, just to show the calculation; that estimation may be well wrong, and is also largely dependent on league, so please check it f you have serious plans with that calculation – when I say to check it, that means, find a match that goes live, with odds similar to ones in this example, and then check FT odds at half time. So, if prematch 1X2 odds were 1.40 / 4.60 / 6.75, and actual HT result is 1, then I’d say odds for full time at that moment would be 1.15 / 7.00 / 20.00, or probabilities 0.87 / 0.14 / 0.05. If actual HT result is draw, full time odds would be 1.80 / 2.70 / 7.50, corresponding probabilities 0.56 / 0.37 / 0.13. Finally, if actual HT result is 2, FT odds would be 3.40 / 3.00 / 2.30, or probabilities 0.29 / 0.33 / 0.44. Now, you can calculate HT/FT odds. 1/1 = 0.54 * 0.87 = 0.47 -> odds 2.13. X/1 = 0.41 * 0.56 = 0.23, odds 4.41. And so on; check this Excel file for other outcomes: www.betgps.com/files/HT-FT-odds.xlsx (right click and “Save as”, it’s Excel 2007 file, ~20 kB). I estimated FT odds after HT result at overround of about 106%, which is usual overround, and it gives HT/FT overround of 117.7%, while OR of odds in your example is 118.1%, which is pretty close. If you want to check the odds as I suggested, just edit yellow cells, and HT/FT will be updated. I wanted to check if there is a difference if bookmakers’ odds are first adjusted to no overround, so there is another sheet, which first adjust the odds to 100%, and then calculates HT/FT odds, but there is no big difference; it’s on sheet “Without OR”. Though, as Paparazzo said, OR is not evenly distributed between all outcomes, but is usually bigger on underdogs; but to simplify this calculation, I took it as the same for all three outcomes, which probably further adds to inaccuracy. Another possibility to estimate probabilities of FT result after specific HT result is to go empiric way: BetVirus.com (and probably some other sites, as well as my Excel workbook available at www.Betting-Data.com ) will give you actual percentage of all HT/FT outcomes, but they refer to all odds ranges, which will not give brilliant accuracy. So you may want to get yourself historic data available at www.CGMBet.com , which contains HT and FT results and FT odds for some 100.000 matches, filter them for odds range you want (in this example I’d say take range of home odds 1.35 – 1.45), and check frequency (hence, probability) of HT/FT outcomes. You can get the same data from http://www.football-data.co.uk/downloadm.php, too, but they are all in separate workbooks per season and separate sheets per league, while all data from CGMBet are in one single sheet, which makes it a lot easier to do this task.

Quoting user JENSPM The chance of a win is, 1-(A+(B*C)) Where: A = the chance of Marseille winning or grabbing a draw at HT B = the chance of Chelsea winning at HT C = the chance of Chelsea losing the match IF they are winning at HT the correct odds would then be 1/(1-(A+(B*C)))

I have just checked that thread, nice read there; I probably read it before, but forgot, glad to refresh. In post #25, Salford Student suggested the calculation was incorrect, and I think I know why did he say that. If you check post #16, Jenspm calculated C using HT/FT odds; but problem is that you don’t know HT/FT odds – you want to calculate them, so you don’t know them in advance; you know them in this example, because it is what it says – an example; but if you want to use it for real caclulation, you won’t have them in advance. In Excel, it’s called “circular reference”.

I have been reading through www.betgps.com

Thanks for reading! :ok

[Paparazzo]

Re: Soccer Half Time / Full Time odds relationship with HT and FT result? I've made an empirical study analyzing data on the premiership form year 2000 (thanks to football-data.co.uk). In the range of the example the fair odds (based on 412 match with a similar 1X2 odds) will be as follows: [TABLE=width: 114]

[TR] [TD]1\1[/TD] [TD=align: right]2,58[/TD] [TD=align: right]39%[/TD] [/TR] [TR] [TD]X\1[/TD] [TD=align: right]4,58[/TD] [TD=align: right]22%[/TD] [/TR] [TR] [TD]2\1[/TD] [TD=align: right]37,5[/TD] [TD=align: right]3%[/TD] [/TR] [TR] [TD]1\X[/TD] [TD=align: right]18,7[/TD] [TD=align: right]5%[/TD] [/TR] [TR] [TD]X\X[/TD] [TD=align: right]6,75[/TD] [TD=align: right]15%[/TD] [/TR] [TR] [TD]2\X[/TD] [TD=align: right]31,7[/TD] [TD=align: right]3%[/TD] [/TR] [TR] [TD]1\2[/TD] [TD=align: right]137[/TD] [TD=align: right]1%[/TD] [/TR] [TR] [TD]X\2[/TD] [TD=align: right]13,7[/TD] [TD=align: right]7%[/TD] [/TR] [TR] [TD]2\2[/TD] [TD=align: right]18,7[/TD] [TD=align: right]5%[/TD] [/TR] [/TABLE] The value bets in this case are: draw-draw and draw-away. With a 22% chance to win

[gereqi]

Re: Soccer Half Time / Full Time odds relationship with HT and FT result? Thanks Froment and Paparazzo , both your comments and your efforts helped me to better understand their relationship. Was driving me crazy!

[gereqi]

Re: Soccer Half Time / Full Time odds relationship with HT and FT result? Just wanted to thank you again Froment for the clear Excel example you provided, that one explained exactly my point! Thank you so much!