Mathematics and Betting Thread

[kukushkin88]

This forum is probably the most valuable betting resource on the internet. Genuine thanks to all concerned.

[Doobs]

I'd be interested on the mathematics of bad each way races.

How much ev on the win part of the bet can we afford to give up when the place part of the bet is clearly +ev?

I do it by intuition only at the moment.

Here's a calculator

https://docs.google.com/file/d/0Byg8Wbbo5p2uN3dRYlQwaTlhNE0/edit?usp=sharing

you have to download it - you can't put the data in on google docs

I was thinking about putting together a spreadsheet that did calcs like this.  Saves me the trouble.  Thanks

[Doobs]

I assume we can ask questions?

Free bet

Using your theory, is there a point of diminishing return? (Ill assume not, just ever decreasing increase?)

Therefore, although your point is excellent, there must be a point where we say a return is better than bigger ev?

Hence, and where my assumptions lead to, is there a sweetspot price we should aim for?

If you look at the calcs in the free bet post, once you get to 5/1 you have already captured over 80% of the maximum value of the free bet, once you get to 10/1 you have over 90% of the value.  Given you aren't likely to find many genuine 50/1 chances priced at 50/1, there is probably a point where you aren't getting any extra value and just getting more variance from your bets. 

I'd say once you get past 10/1 you aren't going to be able to push much extra return out of your free bet.  In other calcs I have assumed that you lose 10% of the value of the free bet.  To do much better than this you probably have to spend some time analysing form etc.

So if I was to guess at a sweetspot, I'd say about 10s to 12.   Ofc if you find a good 16/1 chance I would just snap it up , regardless, and the same goes for an 8/1 chance you think should be .

[gouty]

Nice read Doobs. You explain quite complex concepts concisely and I have learnt something today which is always a good thing.

Thank you.

[tikay]

Superb thread Doobsy, thank you.

Maybe we could run a little fantasy "Free Bet" Thread, with a fictional bankroll, to see some examples in action.

[outragous76]

cheers doobs

I dont bet much, but your explanations make things really clear.

wpwp on the thread

[Karabiner]

Doobs, I had a situation yesterday where I fancied punting a horse in a good EW race with 18 runners and the best price was 10/1 1-2-3-4 but a couple of firms were paying 1-2-3-4-5 but only offering 8/1.

How on earth can you figure out which of those is better especially when 12.5 was available on betty win only which is what I actually went for?

Of course it came 5th.

[Doobs]

Doobs, I had a situation yesterday where I fancied punting a horse in a good EW race with 18 runners and the best price was 10/1 1-2-3-4 but a couple of firms were paying 1-2-3-4-5 but only offering 8/1.

How on earth can you figure out which of those is better especially when 12.5 was available on betty win only which is what I actually went for?

Of course it came 5th.

Without seeing the shape of the race, or the Betfair place market, it would be difficult to estimate which is better out of 10/1 each way or just backing on the nose on Betfair.   If it is a genuinely good each way race, I suspect it is best to go to the bookies, but it is hard to be definitive about it.

I think it must be the case that 10/1 with first 4 must be better than 8/1 first 5.  The place terms must be worth about the same, but you get better win odds with the 10/1 chance.  I think the race would have to look something like exactly 5 horses under 10/1 and everything else very big prices for the 8/1 and 5 places to be better. 

So I think the choice should have been between betting on the nose, and betting quarter first 4, so you should always lose if you made the best choice.

[Karabiner]

Cheers Doobs, it's nice to know that my instincts were correct.

[doubleup]

re the extra place.  I would think that you aren't going to be that far out if you estimate that mid-longer prices will be placed 5th with the same odds as they would win.

If you think about a genuine 2-1 shot - it will win 33% of time but obv be placed less than 100% of the time, so its placings will be skewed towards 1st place.  As odds lengthen this skewness decreases and likelyhood of being in any position equalises.  Imagine a 20 horse race with every horse of equal ability - they would have an equal chance of placing in every position, so the odds of winning would be exactly the same as placing 5th.

When you move on to genuine outsiders these would begin to be skewed towards last place so the probability of 5th place would be greater than first.

[simonnatur]

"Nigeria's best current forward and likely starter up the front is Aide Brown Ideye. He is best priced 3/1 to be first player to score vs the hapless part time Pacific Islanders, and best priced 1/2 to score anytime.  Bet365 are offering 3/1 and a third the odds each way to score anytime."

I tried to work out EV for backing him e/w as FGS, and started by assuming anytime GS was priced correctly with margin added. Therefore assumed true odds of him scoring anytime are 48%

assuming £1 e/w, so (-2*0.52) etc represents 52% of time he fails to score and we lose our stake...

=(-2*0.52)+(0*(0.48*(1-H2)))+(4*(0.48*))   cell we input % that he is FGS when scoring

IF (big if) I've done this correctly we break even only if he scores first in 55% or more of the matches in which he is a goal scorer

[Doobs]

"Nigeria's best current forward and likely starter up the front is Aide Brown Ideye. He is best priced 3/1 to be first player to score vs the hapless part time Pacific Islanders, and best priced 1/2 to score anytime.  Bet365 are offering 3/1 and a third the odds each way to score anytime."

I tried to work out EV for backing him e/w as FGS, and started by assuming anytime GS was priced correctly with margin added. Therefore assumed true odds of him scoring anytime are 48%

assuming £1 e/w, so (-2*0.52) etc represents 52% of time he fails to score and we lose our stake...

=(-2*0.52)+(0*(0.48*(1-H2)))+(4*(0.48*))   cell we input % that he is FGS when scoring

IF (big if) I've done this correctly we break even only if he scores first in 55% or more of the matches in which he is a goal scorer

If you start by assuming the odds we get on our place part of our each way price is the correct one, you are a long way on the road to proving the bet is terrible. BUT we only got evens on the anytime scoring because we are backing each way, and they are using standard pricing rather than adjusting to this particular match.  The odds quoted elsewhere on him scoring anytime are either 1/2 or worse.  That is equivalent to scoring in 67% of matches. Obviously 67% is likely to be a bit too high, but the true odds are going to be a lot closer to that than 48%.



 

[Dubai]

He is probably around 7/2 15/4 1st gs and 8/13 4/7 anytime

[Doobs]

He is probably around 7/2 15/4 1st gs and 8/13 4/7 anytime

I did a calc last night and think the bet was still quite profitable if the true odds were 7/2 and 4/6.  Am rushing out, so can't check this now

[RickBFA]

This looks like a great thread. Really useful, thanks.

Looking forward to your thoughts on dirty each ways.