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Old 05-15-2019, 05:46 PM   #1
rdiam
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Ex Ante and Ex Post

There continues to be confusion among several posters between what is referred to as Ex Ante and Ex Post thinking. It important to understand the difference:


Ex Ante means "before the event". When you bet on horses or make any other kind of prediction, you are doing so "ex ante"; that is, you have to make your bet BEFORE the race is run. Kind of obvious.


Ex Post means "after the event". After the race is run, there is only 1 winner (assuming no dead heat) "ex post"; that is, the winner has a win probability of 1.0 and all of the other horses in the race have a win probability of 0.0. Again, kind of obvious, but unfortunately, you generally cannot bet a race after it has been run (assuming nothing devious like past posting).


So those who insist that you need to pick winners are right -- ex post. Buying a lottery ticket (a horrible -EV bet with the possible exception of a large carryover) loses you money EX ANTE, but if you win, it was the RIGHT decision EX POST.


Since we have to bet before the race is run, we need to deal in probabilities. Every horse has some chance to win the race -- some more than others. We need to focus on making the right decision with the information we have available to us, NOT on making the perfect decision.


Win percentages matter, but so do odds. It is the combination of these that determines whether we are betting with an edge (+EV).


What if I gave you a system that hit, on average, 40% winners betting 1 horse a race? A show of hands, please. Sounds like a good deal. Now, what if that system produced the 40% winners at average odds of 6/5? Lots of winners, but -EV (for those mathematically challenged, the breakeven odds for such a system is 3/2).


The system, by the way, is to just bet the tote board favorite...


Bottom line, it is important to differentiate between ex ante and ex post thinking. Sure, you need to pick a winner to cash a ticket, but that is ex post thinking. Better off using ex ante thinking which understands that mathematically we must bet at +EV. Certainly, every professional bettor understands this concept, and do their best to avoid -EV wagers. Casino hotels are built on trying to provide only -EV bets to patrons. Think ex ante, not ex post.


Richard
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Old 05-15-2019, 07:06 PM   #2
Mitch44
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Richard:
Race tracks are not casino's and they don't determine odds a horse goes off at. They only act as a caretaker of the money,for a commission.Casinos have fixed probabilities whereas horseracing does not.

Years ago you're theory had more merit however in todays racing that has diminished greatly, the game has changed dramatically with so much late money that EV is unpredictable. Also the public is not predicable.

I find the same problem with tote board watchers. One has absolutely no idea where that money is coming from and whether its smart money or uninformed tipster money. To me those that rely on such things have a hole in their game and lack confidence, seeking a confirmation for their decision.

Try playing a P3 or P4 etc. with only expected high EV horses and see how many are cashed. Legitimate low EV horses must be included in any sequence of bets. Additionally its impossible to know the EV when playing multiple race bets.

The game all comes down to picking winners prior to the bell or EX Ante, theory or Ex Post pays nothing.Winners are the gold standard and springboard for every bet. The player should design the bet to take advantage of their EX Ante assessment.

Mitch44
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Old 05-15-2019, 08:00 PM   #3
rdiam
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You are stating the obvious that one needs to pick winners (as opposed to place or show horses) in horizontal bet sequences such as DD, P3, P4, etc. As I have frequently stated in other posts on this board, there are some races that will be part of such a sequence that are quite predictable, and other races that are more open or less predictable. In fact, in such predictable races, they are likely to be won by the first or second public choice, and it would be folly to leave them off of your horizontal bet ticket.

But betting a P3 or P4 sequence with ALL "predictable" type races will be -EV, even without knowing the payoff. At an extreme, if you bet the top 2 ML choices in each race, you will cash a lot of P3 or P4 tickets, but the payoff will not cover your loses. Lots of obvious winners, but the takeout and overbetting of these combinations will kill you.

As you know, the goal of a horizontal bet is to improve on your payout versus betting a parlay and having the track take deducted from each race. Since you like to test things, take a look at daily doubles where the sequence is a predictable race (likely to be won by the top 1 or 2 betting choices) followed by an unpredictable race (unlikely to be won by the top 1 or 2 betting choices). Since I have done the research, I will save you the time: you will be hard pressed to find a DD payout that exceeds the parlay payout.

Conversely, if you bet the sequence in a DD where the first race is unpredictable and then second race is predictable, your DD payoff will almost always beat that of a parlay bet. Why? Because most will cover the first race with the vulnerable favorite or second favorite in the DD, so you get the advantage in that pool when they do not win. And there is no real need to see the odds of the horses in the second race, since you figure that only 1 or 2 has a real chance to win anyway.

Sure, it is hard to "know" the closing odds these days with the simulcast dump. But just because it is hard doesn't mean you should not try to make an estimate. I am sure, with your experience, you can estimate final odds of most horses at tracks you frequently play. And I am positive you can tell when the ML is way off based on your own knowledge. We play a game of decision making under uncertainty. Estimation of variables is part of the game. Precision is nice, but not always required.

Finally, I don't really know you except from this board (but hope to meet up in August at SAR), but I do know and have been a part of successful betting syndicates in both horse racing and sports. They are ALL price sensitive and deal in probabilities: if the race was run 100 times, how often will each horse win? Pari-mutuel betting with simulcast dumps makes it difficult, but not impossible to estimate whether they are getting paid to take the risk.

Don't make the mistake of thinking any winning bet is a "good" bet. That is ex post thinking. If you are not getting paid to take the risk (i.e., there is a probability of the horse losing = 1 minus it's win probability) you pass.

Finally, all of the professional bettors use a form of Kelly Criterion betting. They do NOT look for each individual horse to be "value", as you put it. They look +EV of the group of horses they are betting. So in your P3 example, they will certainly include "obvious" horses in the group, as long as there is a healthy mix (via the math) of underbet horses as well. That is the beauty of Kelly: by including some slight "underlays" you will increase your win % enough to grow your bankroll faster since you can bet bigger (fewer losing streaks), even though your ROI is reduced. Real value betting is all about estimating win probabilities, NOT JUST betting so-called "overlays."


Richard
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Old 05-16-2019, 12:32 AM   #4
Mitch44
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I find that as a handicapper,figuring what the public may do to is very unpredictable.Horses with a M/L of 3-1 paying $20 and horses 20-1 bet down and paying 5-2. Go figure.

I do agree that money management is the Achilles heel for many players because they fail to address it. Its a major component of success,and how one structures their bets. Also one must capitalize on the public mistakes when they do make a mistake, you have to be good to do that.

Many good priced horses come from following a consistent procedure of approach while the public flails around like a fish out of water.

I don't see EV as the answer to poor handicapping. No EV will make a winner out of poor selections. Period! Even the Kelly can't help someone that can't even pick their nose. Positive expectations come from good handicapping and outperforming your adversary or the public in this case.

Mitch44

Last edited by Mitch44; 05-16-2019 at 12:34 AM.
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Old 05-16-2019, 12:39 PM   #5
rmath
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Bravo Mitch.
I agree with you completely.
I never heard Doc or Jimmy ever say anything about + or - EV.
You find the main contenders and then you bet according to the post time odds.
If the odds are too low you pass and wait for the next race.
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Old 05-16-2019, 01:24 PM   #6
Lt1
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I have showed a profit every year since 1998 following the Docs guidelines. To be honest I never heard the terms EV, Ex Ante, or Ex Post before Richard shared them with the group. When I was working with handicapping service it seemed to me that the whales were more interested in rebates then actually winning races. Maybe they have changed their approach AS for me, for now, I'll just continue to keep it simple and follow what I learned from Doc when it comes to wagering.
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Old 05-16-2019, 01:53 PM   #7
Jeebs
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Excellent discussion on value.

Since parimutuel betting is a fluctuating market, some races/tracks are more sensitive/prone to price changes more than others. It’s a factor worth considering in your play.

Attempting to assign probabilities to each CONTENDER is a difficult task. Record keeping may simplify it somewhat, but it is still a guessing game.

When using Sartin methods for paceline selection, we’re provided by default, a range of lines in which to choose. Some are more comparable than others, while some are not comparable at all. Regardless of your method, the line selected should show potential in a contender matchup. Ancillary factors that are not pure “Sartin” also should be considered in the context of value to further narrow the scope. I hope that this makes sense.
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Old 05-16-2019, 04:04 PM   #8
Mitch44
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Jeebs;


It makes sense to me and your correct.

I use to take 9-5 and can make a profit on that. The lower the odds one accepts the higher win percentage you must obtain to show a profit. Now I try to look at alternatives to taking that, such as an EX etc. and even with that I try to avoid low paying EX., especially combinations of the lowest 2 odds horses. I don't even have to look at the Ex matrix to see what they'll pay as I know their unacceptable. The public frequently makes the mistake of hammering some EX payoff down to $7.Thats insane to take. This also reduces the extension of my bet (capital put in) so when I do hit I win more and when that low paying EX of the two low odds horses does beat me I risked less, again helping my overall profit. Generally the public is good picking a winner but lousy on EX or DD. They fail to take advantage of the DD and reducing the take out but will bet to win in two connecting races. Love those rolling DD races.

I still use the 60-40 on the low odds horse and 40% on the longer odds horse. I also reverse the 60-40 so if the low odds horse wins I break even or about even and if the longer odds of my two wins I have 60% on it. This really comes down to how much you trust your opinion and assessment and what the public is giving you. I don't have a problem breaking even on a race.There are many ways to design bets.

The bottom line is I try to design a bet based on my assessment of the race and to also take advantage of the public's mistakes based on my assessment. Always looking for a profit and getting value for my money based on overlays created by the public's mistakes. Design the bet to fit your analysis and seize the moment to exploit and capture their mistakes.

Its also helpful to be able to tune out the noise and stick to your analysis. I pay little attention to the M/L and other so called expert picks. Odds never scare me and once a decision is made I don't care if its 100-1 I'm still betting it. To reap the rewards one must make the bet, far too many get scared off good paying horses.

It takes great discipline but the best option for most and what I would recommend is to pass a race where the odds are too low on your choices. As Tim(Lt1) says "no one ever loss money passing a race." There also is another one coming along in 20 minutes or so.

Mitch44
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Old 05-16-2019, 05:17 PM   #9
Bill V.
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Right on

Quote:
Originally Posted by rmath View Post
Bravo Mitch.
I agree with you completely.
I never heard Doc or Jimmy ever say anything about + or - EV.
You find the main contenders and then you bet according to the post time odds.
If the odds are too low you pass and wait for the next race.
Rmath
MITCH, Tim and Rmath , i already mentioned my success, I have seen you 3 win at master level for years, I laugh when I try to imagine you not making bets because of some math equation
The methodology builds within us the ability to bet for a profitplain and simple
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Old 05-16-2019, 06:57 PM   #10
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Hi Bill. Glad to see you are able to post. Thanks for the kind words. I admit that I would have a hard time applying a math equation before making a bet. It may well be the proper way to bet but it's not for me. Until such time that what I do no longer is profitable I'll stick with what the Doc taught us. Be well my friend and I'll see you at the Spa.
Tim
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