Laying System Advice

[bradw]

I have been working on a system for laying horses and need some advice.

My database has provided the following approximate infomation when backing the selections for a win over the last year (every raceday):-

2000 selections
17 % strike rate
31% Loss on Turnover.

My thinking is that this would make a good laying system.

Any advice on what further testing I should complete.

Brad

[odericko]

i may be a cabshazed minda but i can see that if you wish to lay you have to be at the screen and get the lowest price ...i always thought i couldnt pick a winnerr to save my miserable life then along came betfair....bollocks picking a loser is harder by a long shot dont doit """ laying is for chickens''

[bradw]

if you wish to lay you have to be at the screen and get the lowest price ...''
I intend to use one of the Betfair Automation Tools to place bets just before racetime with some price parameters.

[AngryPixie]

Bradw

What's the average and median SP's for all selections, all winners and all losers?

[bradw]

Bradw

What's the average and median SP's for all selections, all winners and all losers?
All - Average - $8.97 Median - $5.70

Winners - Average $4.00 Median - $3.40

Losers - Average $9.97 Median - $6.50


BradW

[AngryPixie]

Bradw

On the figures supplied I think you'd have a negative expectation of about 6.5%. We should really be using the sum of the chances of all selections, not their average SP, but this is close enough.

Observed successful lay selections =
Total Lays * (1-Win SR) = 2000*(1-.17) = 1660

Expected successful lay selections =
Total Lays * 1-(1/Average SP all selections) = 2000*1-(1/8.97) = 1777

Advantage = (1660/1777)-1 = -0.0658

What this is telling us is that you should have had 117 more successful lay bets than the 1660 observed based on the average SP of all your selections. So in the long term you could expect to lose $0.0658 for every lay doller risked. You need to find a way of getting your lay strike rate up without increasing the average SP of all selections, or try to reduce the average SP of all selections whilst maintaining your strike rate. :(

Please somebody else check this as it's getting late and I've had a crap week.

[bradw]

Pixie,

Thanks for your calculations.

I understand what you are getting at with the formulas. But if I had laid each runner I would have returned a nice profit.

I don't believe you can use the SP as the true chance of each runner. The market is a good indication but not 100% accurate.

BradW

[AngryPixie]

Thanks for your calculations.

No worries. You don't say whether your prices were at SP or were Betfair prices. You'll have a better chance if they were from Betfair, but if they were SP your a bit b_uggered I think.


But if I had laid each runner I would have returned a nice profit.
I don't believe you can use the SP as the true chance of each runner. The market is a good indication but not 100% accurate.

No it's not 100% accurate and it doesn't have a memory either. So what would have happened is not what will happen in the future. As far as accuracy goes I believe it's as close as your going to get :)

Hope it works for you. Love to hear how it goes. Why not post a week or two of selections up here.

[bradw]

Hope it works for you. Love to hear how it goes. Why not post a week or two of selections up here.

Would happily provide selections to the list except the method really has only 2 rules and one is extremely obvious and others could work it out it under 2 mins.

[bradw]

Have just done a little finetuning and only betting on Wed & Sat get the following data :-


Observed successful lay selections =
Total Lays * (1-Win SR) = 427*(1-.13) = 371
Expected successful lay selections =
Total Lays * 1-(1/Average SP all selections) = 427*1-(1/10.21) = 385
Advantage = (371/385)-1 = -0.036

Brad

[AngryPixie]

Brad

That looks a little better, but remember if these are SP prices you'll be about 5-20% worse off when you strike a winner when laying on Betfair.

You seem to have a wide variation between your average and median prices so you must be laying some real long ones. You might try filtering on price not days. Also you could watch the market moves and avoid the ones that shorten dramatically in the last twelve minutes or so of betting.

[SeeDee]

Brad

Also you could watch the market moves and avoid the ones that shorten dramatically in the last twelve minutes or so of betting.AP, do you mean avoid the individual runners or the entire race where this occurs altogether?

[AngryPixie]

Individual runners. I think Chrome uses a similar tactic.

[AngryPixie]

Brad

How are you getting on?

[bradw]

Thanks for asking Pixie.

I have been getting my Betfair account setup (ID Check) and am away on holidays for a week or so. Once I get back home I will commence on my laying journey.

BradW