

09122021, 04:55 AM

#1

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Join Date: Feb 2019
Posts: 423

estimating fair exacta payouts
__________
every writer I've ever read on this subject states that this is the correct way to do it is this  or something very similar to this:
9/1 over 11/1_________9*11 +(1) = $108_______for a $1.00 exacta
but isn't it true that a 9/1 shot over a 11/1 shot will usually pay much more in a 12 horse field than a 5 horse field?
I don't recall any of the discussion of this including field size
it would probably be very difficult or maybe even impossible to prepare a matrix which factors in field size
I certainly couldn't do it_________I'm not a mathlete
but, in all the writings I've seen on this subject field size was never mentioned
so, if it's not considered aren't the writings on this, unless they mention or consider field size, lacking?
.
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believe only half of what you see.....and nothing that you hear..................Edgar Allan Poe



09122021, 11:03 AM

#2

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Join Date: Mar 2007
Posts: 1,252

Quote:
Originally Posted by Half Smoke
__________
every writer I've ever read on this subject states that this is the correct way to do it is this  or something very similar to this:
9/1 over 11/1_________9*11 +(1) = $108_______for a $1.00 exacta
but isn't it true that a 9/1 shot over a 11/1 shot will usually pay much more in a 12 horse field than a 5 horse field?
I don't recall any of the discussion of this including field size
it would probably be very difficult or maybe even impossible to prepare a matrix which factors in field size
I certainly couldn't do it_________I'm not a mathlete
but, in all the writings I've seen on this subject field size was never mentioned
so, if it's not considered aren't the writings on this, unless they mention or consider field size, lacking?
.

It is 1081 or $109 for $1 not $108. These are based off of fair value assessment not the actual odds of the horse. The number of runners in a field is already incorporated into you fair line estimation, because you assign an odds line to each horse. So even if you have 3 horses you make 501 in the race they still eat up 6% of your odds line and you only have 94%(points) to give to the rest of the runners. Also some might make a fair value place line, because some horses are more apt to run 2nd than win, some horses are feast or famine types......
Of course all of this is theoretical. If you can't make money lining a race and betting horses you make 41 when they are 61 or higher, you aren't going to start making money because you are playing exactas that should pay $21 based off of your line that are paying $35. The bottom line is you can line races until you are 100 years old and doing so will help you at least isolate "value" plays in your mind from non value plays(which might help to some degree). But it will only make you a winner if you can make a fairly accurate line and that it is much easier said than done. Also exacta prices are subject to the same after the bell adjustments that win prices are so just like that horse you bet at 41 that gets hammered to 5/2 after they are off so does that exacta that you rated to pay $8 is paying $12 and ends up paying $6.60.
Regarding your point about exactas paying better in large fields than in small fields, I think that is the nature of the beast. If you have a 20% take on say 110 exacta combinations instead of on 20 it seems pretty logical you will get better payoffs on 11 horses fields instead of 5 horse fields.



09122021, 11:26 AM

#3

Loitering with intent
Join Date: Jan 2006
Posts: 26,477

Quote:
Originally Posted by Half Smoke
__________
every writer I've ever read on this subject states that this is the correct way to do it is this  or something very similar to this:
9/1 over 11/1_________9*11 +(1) = $108_______for a $1.00 exacta
but isn't it true that a 9/1 shot over a 11/1 shot will usually pay much more in a 12 horse field than a 5 horse field?
I don't recall any of the discussion of this including field size
it would probably be very difficult or maybe even impossible to prepare a matrix which factors in field size
I certainly couldn't do it_________I'm not a mathlete
but, in all the writings I've seen on this subject field size was never mentioned
so, if it's not considered aren't the writings on this, unless they mention or consider field size, lacking?

I've seen these calculations too...and they've never made any sense to me. When you multiply the odds of the winner to those of the runner up...you get the exact same total as if the race outcome were reversed. A 21 winner and a 101 runner up pays the same as a 101 winner and a 21 runner up. Which, of course, is RIDICULOUS.
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09122021, 11:53 AM

#4

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Join Date: Mar 2007
Posts: 1,252

By the way Half Smoke is correct, $108, not $109. The math is pretty simple probably not very accurate in the extremes probably more accurate in the middle range(say with 31 to 81's).. Take a horse you make 11 over a horse you make 31. 11 over 31 should pay $4 (1*3)+1=$4. or (3*1)+3=$6. 11 has a 50% chance of winning 31 has a 25% chance of winning. 50% chance 11 wins, should he win the 31 would have a .25/50 or 50% chance of coming 2nd. 50% * 50% is 25% chance of the 11 over 31 exacta coming in or fair price of $4 for a $1. Should the 31 win .25 there is theoretically a .50/.75 .667% chance of the 11 coming second. .25*.667 or about 16.67% of the 31 over 11 exacta coming in or 51 fair odds or $6.
Why is it inaccurate? Horses on the low end of the odds board, say 3/5 shots, even if you can accurately assess their fair odds value, I am pretty sure you will find that they will not come in 2nd as likely as the assumptions in this formula lays out. In other words in the above example, the 11 doesn't not actually have a .667 % chance of coming 2nd should the 31 win, imo. On the high end I think you will have horses coming 2nd more often than they should. I am sure the whales have the correct formulas, I don't. I am to busy trying to figure out why the horse I make 6/5 is going off at 2/5 and winning under wraps



09122021, 12:18 PM

#5

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Join Date: Feb 2019
Posts: 423

___________
this is only one example and of course proves nothing  still kind of interesting
race 11 yesterday KY Downs  9/1 over 11/1 paid $175  an 11 horse field
when I saw that I went back and looked at some races at Saratoga, IIRC this race wasn't from yesterday, anyway
I don't have it at hand to link but I saw a race in which a 37/1 over a 16/1 paid only $217 in a 7 horse field
Thaskalos's point is a great one  I was going to mention that but he beat me to it
https://www.equibase.com/premium/cha...1&cy=USA&rn=11
.
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believe only half of what you see.....and nothing that you hear..................Edgar Allan Poe
Last edited by Half Smoke; 09122021 at 12:30 PM.



09122021, 12:32 PM

#6

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Join Date: Mar 2007
Posts: 1,252

If you line races (and you don't even have to make your own lineyou can use the final odds/1.17 to get a correct fair odds line and probably would be better for the excercise I am laying out). Calculate the fair exacta prices and fair double prices and look at the final payoffs. Do so on a number of races and you will see betting biases. Which combos are close to fair value, which are far lower? Any paying better? You can probably learn something that will help you make better decisions in the future.



09122021, 03:14 PM

#7

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Join Date: Nov 2012
Posts: 1,035

The rule of thumb is win price of the winner multiplied by place price of the runner up. So for example looking at Woodbine today race 4, winner paid $5.20 and the place horse $7.20, multiply those and you get $37.40 for the exacta and it paid $36.10.
More rules of thumb, the place price is ballpark 40% of win odds to the $1.
If you're looking at an 8/5 horse should pay $5.20 in the win slot. Place horse was 101, 40% of that is $10 to place, it only paid $7.20 however it ran second to the favorite so that would have to be part of the place estimate.
In other words 40% of 101 is an overall ballpark number, it doesn't accurately estimate the likely place payoff when paired with the favorite, which you would need to do if you want to pinpoint place payoffs. I've never dug into it more deeply but you might be able to use that as a starting point anyway.
Last edited by MJC922; 09122021 at 03:28 PM.



09142021, 06:53 AM

#8

what an easy game.
Join Date: Dec 2002
Posts: 40,131

THE EXACTA MATRIX HAS BEEN MY HOBBY,
THE PROBABILITY OF A HORSE WINNING IS (1/(ODDS+1))/ THE RACES TOTAL BOOK PERCENTAGE .
THE TOTAL BOOK PERCENTAGE FOR A TRACK WITH A 15% TAKE OUT SUMS TO ABOUT 1.18
THE PROBABILITY OF ANY HORSE WINNING IS (1/(ODDS+1))/1.18
TAG THE WIN HORSES WIN PROBABILITY WITH "A"
TAG THE PLACE HORSE WIN PROBABILITY WITH "B"
EXACTA PROBABILITY PROBABILITY FOR A/B IS:
A X (B/(1A))
EXAMPLE: A HORSE ODDS =21, B HORSE ODDS = 31, TRACK TAKE OUT IS 15%
A HORSE WIN PROBABILITY IS (1/(2+1))/1.18 = .282
B HORSE WIN PROBABILITY IS (1/(3+1)/1.18 = .212
PROBABILITY FOR THE A/B COMBINATION IS,
.282 x (.212/(1.282)) = .083
THAT EQUATES TO A $1 RETURN OF (1/.083)= 12.04
THE FAIR $1 PAYOUT IS $12.04
IN EXCEL FORMAT:
Last edited by formula_2002; 09142021 at 06:59 AM.



09142021, 11:40 AM

#9

what an easy game.
Join Date: Dec 2002
Posts: 40,131

Quote:
Originally Posted by MJC922
The rule of thumb is win price of the winner multiplied by place price of the runner up. So for example looking at Woodbine today race 4, winner paid $5.20 and the place horse $7.20, multiply those and you get $37.40 for the exacta and it paid $36.10.
More rules of thumb, the place price is ballpark 40% of win odds to the $1.
If you're looking at an 8/5 horse should pay $5.20 in the win slot. Place horse was 101, 40% of that is $10 to place, it only paid $7.20 however it ran second to the favorite so that would have to be part of the place estimate.
In other words 40% of 101 is an overall ballpark number, it doesn't accurately estimate the likely place payoff when paired with the favorite, which you would need to do if you want to pinpoint place payoffs. I've never dug into it more deeply but you might be able to use that as a starting point anyway.

my calculations



09142021, 04:51 PM

#10

what an easy game.
Join Date: Dec 2002
Posts: 40,131

Quote:
Originally Posted by MJC922
The rule of thumb is win price of the winner multiplied by place price of the runner up. So for example looking at Woodbine today race 4, winner paid $5.20 and the place horse $7.20, multiply those and you get $37.40 for the exacta and it paid $36.10.
More rules of thumb, the place price is ballpark 40% of win odds to the $1.
If you're looking at an 8/5 horse should pay $5.20 in the win slot. Place horse was 101, 40% of that is $10 to place, it only paid $7.20 however it ran second to the favorite so that would have to be part of the place estimate.
In other words 40% of 101 is an overall ballpark number, it doesn't accurately estimate the likely place payoff when paired with the favorite, which you would need to do if you want to pinpoint place payoffs. I've never dug into it more deeply but you might be able to use that as a starting point anyway.

misread your odds .
minimum $1 return for that play was $52.30, it returned only $18.05
Last edited by formula_2002; 09142021 at 04:54 PM.



09152021, 08:15 AM

#11

Registered User
Join Date: Feb 2019
Posts: 423

__________
re calculating a exacta payout:
the actual payout is often not even remotely close to the fair payout as indicated in my earlier examples
then how about calculating a fair tri and superfecta payout
I'm sure it can be done
but I'm all but sure that many of the actual payouts won't be anywhere near the calculation of the fair payout
.
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believe only half of what you see.....and nothing that you hear..................Edgar Allan Poe
Last edited by Half Smoke; 09152021 at 08:16 AM.



09152021, 12:27 PM

#12

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Join Date: Oct 2001
Location: near Lone Star Park
Posts: 3,982

I wrote a program to calculate the fair exacta prices on boxing up to 7 horses.
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Ranch West
Equine Performance Analyst



09152021, 02:38 PM

#13

what an easy game.
Join Date: Dec 2002
Posts: 40,131

Quote:
Originally Posted by ranchwest
I wrote a program to calculate the fair exacta prices on boxing up to 7 horses.

My kind of guy.
The only way I can calculate the fair odds is by using the results charts to determine final win and exacta payout and the racing booking percentage.
then I convince myself i should stay with the pass line at craps (1.14 vig)
Good luck in all your endeavors



09152021, 04:37 PM

#14

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Join Date: Oct 2001
Location: near Lone Star Park
Posts: 3,982

My program uses the odds that the user inputs. Anyone should be able to operate it. Just enter up to 7 odds values, that's it.
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Ranch West
Equine Performance Analyst



09152021, 05:00 PM

#15

what an easy game.
Join Date: Dec 2002
Posts: 40,131

Quote:
Originally Posted by ranchwest
My program uses the odds that the user inputs. Anyone should be able to operate it. Just enter up to 7 odds values, that's it.

I download (cut and pasted now) the wps and exacta tote board data into an excell file then ctrl "k" ctrl "f" and I have the current calculated fair exacta values for every runner cobination. I can then compare current fair values to the current exacta payouts.
Hint: at this time (after about 25 years), I consider it a hobby!!





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