Exacta betting helped by iPhone Apps?

[Jimboy]

When I search the Apple App store with"exacta betting", two or three apps pop up. Some compute the "fair" exacta payout based on all the horses odds. I also found a web site hat does a similar thing. Has anybody out there tried these? Will I be wasting my time, or is there an edge in knowing the "fair" payoff and looking for overlays?

 

[Jimboy]

Nobody out there using apps for betting?

 

[G.MONEY]

I never even thought about looking for a app like that, not sure what fair value is, with the different take outs at all tracks, it is not easy

 

[Jimboy]

G.Money, the app ExactaBet, for example, defines "fair" odds as what the odds or payoff for an exacta should be if it was calculatd from the odds of the individual horses odds, using probabilities formulas (instead of using the exacta betting pool). Thats what they say in the app description in the Apple AppStore anyway...
so I was wondering if any body was using this stuff? And if so, any luck?

 

[Prof_Factor]

http://www.horseracinggold.com/Exacta payout chart.htm

 

[Jimboy]

Prof, it looks like you have studied or looked into the " fair payoff" for exacta bets problem. Thanks for the link and info!
my criticism of the "fair" odds in the chart in the link is as follows:
One picks the exacta horses odds and goes down to the second horses odds to get the exacta odds. This means that you only take in account the two horses involved. In the apps description in the AppStore (ExactaBet) it clearly states that you need to enter the odds for all the horses in the race or he calculations will be off. That makes sense to me, especially if there are several horses with low odds, for example. If it makes a difference in actual play i have no idea...
Thanks again for the link, Prof.

 

[Prof_Factor]

The only reason you would need to enter all the horses odds is so the app can determine Takeout rate involved.
Then that alone tells you it is not using Probability odds to determine fair value. It is using takeout in its calculations to determine expected payout and then a value pay from that. Has nothing to do with probability unless all odds are true odds and that is impossible with takeout.
Hope that makes sense.

 

[Jimboy]

It does make sense, Prof. They could compute the takeout rate from the odds of all the horses. However, after digging deeper, looking at the ExactaBet support web site, I found that the odds for each horse are used in probability calculations for exacta payoffs. They use a formula developed by a Dr. D.A. Harville. I googled the formula, and you have to use the odds for each horse.

 

[Prof_Factor]

If you are inputting odds from a toteboard, then they are not calculating probability based on true odds.
I don't know anything about the app or the formula involved, but would not waste my time inputting odds to try and find exacta overlays. Especially toteboard odds that fluctuate in the closing minutes.

Exacta probability = Win probability x Place probability.
Maintain 100% probability for each event.
When we know the winner, and it's win chances, we know remaining field's chances to run 2nd once we adjust back to 100% probability.
example, (working with true odds probability/percentages not payoffs)

Field (true odds to win)
-----         
.20 (5-1)
.20 (5-1)
.20 (5-1)
.20 (5-1)
.10 (10-1)
.10 (10-1)
====
100%

Lets say winner was a 5-1 shot with 20% chance to win and the rest of the field had 80%.
Adjust Place probability to 100% with remaining field.

Field (chances to place)
-----         
winner removed
.20/.80 = .25 (4-1)
.20/.80 = .25 (4-1)
.20/.80 = .25 (4-1)
.10/.80 = .125(8-1)
.10/.80 = .125(8-1)
          ====
          100%

If the winner was one of the 10-1 shots then the rest of the field had 90% win probability.
Adjust Place probability to 100% with remaining field, like we did before.

Field (chances to place)
-----         
.20/.90 = .222 (9-2)
.20/.90 = .222 (9-2)
.20/.90 = .222 (9-2)
.20/.90 = .222 (9-2)
winner removed
.10/.90 = .111 (9-1)
          ====
          100%

exacta probabilities based on true odds:
5-1 with 5-1 = (.20x.25) = 20-1
5-1 with 10-1= (.20x.125) = 40-1
10-1with 5-1 = (.10x.222) = 45-1
10-1with 10-1= (.10x.111) = 90-1

 

[Lt1]

I don't know about probabilities but I do know that the top 2 public betting choices historically run 1 -2 only about 24% of the time and usually don't pay well. When I want to determine what the ex should pay I add 1 point to the horses odds ex 3-1 with 4-1 would be 4x5 = 20 x 2 = $40. Granted it's a dirty process but works well enough for me amd keeps me off low paying combos.

 

[Prof_Factor]

I don't know about probabilities but I do know that the top 2 public betting choices historically run 1 -2 only about 24% of the time and usually don't pay well. When I want to determine what the ex should pay I add 1 point to the horses odds ex 3-1 with 4-1 would be 4x5 = 20 x 2 = $40. Granted it's a dirty process but works well enough for me amd keeps me off low paying combos.

That is exactly the same method I would use!! Thanks for posting .

 

[Jimboy]

Prof, I agree with all your calcs in the example. You also used all the horses odds in the race. So I think the conclusion is that if you can estimate the odds of each horse, and have some way of doing the calclations before growing old, you have a fair chance of spotting overlays. Would you think my conclusion is close to correct?

 

[Prof_Factor]

I actually posted entire fields to prove it is not needed.
Only the win and place horse odds are used in my example.
The entire field is used only to proof check that event probability total 100% after adjustment formula is applied.
Same numbers result with just 2 horses odds.

But yes, I agree you need a quick method. I suggest Lt1's approach.
I would also use my posted method to create an exacta line from a value line.

 

[Jimboy]

Prof, was referring to your large example with the 5 to 1 and 10 to 1 probabilities. There you clearly use all the horses probabilities in the denominator. For example, for the place calc, you add up .20,.20,.20,.10,.10 to get .80 .
In your short example, using odds+1 times odds place +1, you only use two horses. Problem with this is that you get the same result for a 5 to 1 with a 10 to 1 as you would with a 10 to 1 with a 5 to 1. OK if the odds are closer together probably.
So I would use the short version if I did not have an iPhone. Snce I have an iPhone I would use long version with an app like ExactaBet.

 

[Prof_Factor]

Prof, was referring to your large example with the 5 to 1 and 10 to 1 probabilities. There you clearly use all the horses probabilities in the denominator. For example, for the place calc, you add up .20,.20,.20,.10,.10 to get .80 .In your short example, using odds+1 times odds place +1, you only use two horses. Problem with this is that you get the same result for a 5 to 1 with a 10 to 1 as you would with a 10 to 1 with a 5 to 1. OK if the odds are closer together probably.So I would use the short version if I did not have an iPhone. Snce I have an iPhone I would use long version with an app like ExactaBet.

Actually I don't add up the field ..... I subtract the winner's prob from 100 .... which equals the remaining field total.

With the other method, you are exctly right, it won't be dead accurate. But it is quick.

 

[Jimboy]

Ok, Prof, I think I understand now. You dont need all the horse odds if you use the ideal probabilities in your long example. If you use the odds from the tote board, you need odds for all the horses so that you can account for the takeaway, which can be up to 25%, depending on the track. That is probably why ExactaBet uses all the odds. Thanks for the very clear examples!