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Old 07-15-2018, 10:29 PM   #31
JeremyJet
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Originally Posted by JerryBoyle View Post
If those are the scores for 4 races, that is possible. The score I posted is the mean of scores over 6024 races. Within that sample of 6k races, there are some (105) with scores within the range you've posted. However, if your scores are consistently as you've posted, whatever model you're using is significantly better than mine .

EDIT: over those 6k races, the public's final odds line using the win odds converted to probabilities had a brier score of .7698
What do the numbers mean, though? Race 1 had a Brier Score of .099. Does that mean the line for that particular race was 90.1% accurate?
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Old 07-15-2018, 10:48 PM   #32
JerryBoyle
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What do the numbers mean, though? Race 1 had a Brier Score of .099. Does that mean the line for that particular race was 90.1% accurate?
I'm not sure there is an intuitive interpretation of the # by itself. By definition, it's the sum of the squared error of your predictions for that race. The difficulty in interpreting the # by itself is why I mentioned that you should only interpret it relative to other scores, and probably only averaged over many races.
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Old 07-16-2018, 05:46 AM   #33
highnote
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Trying to add another weapon in my arsenal. I have been a bit more selective on what races I wager the past few months. Fewer wagers have resulted in more profit at the end of the wagering day.

Now I want to really concentrate on my pick and only wagering if there is value instead of just wagering to pick a winner. My question is this: For those of you that only bet if you think the horse has value, meaning he is 4/1 and should be 2/1, is how do you determine if the horse should be 2/1?

I need a bit of help in that area and any suggestions would be much appreciated.
I got my start from reading books by Dick Mitchell. Lots of timeless info in his books -- especially on the mathematics of racing.

He gave computer code for his software programs in his books, so you could type in the BASIC language code and run his software on your computer.

That's where it all begins -- with simple little programs. You build on it from there. The code I write today is much more complicated than the ones in Dick's Mitchell's old books, but some of the fundamental concepts are the same. You can probably find code that will turn your handicapping factors into an oddsline.

I wrote some software for an old friend that would create an oddsline using his speed figures by entering them into a monte carlo simulation. If he put in good figures he got out good probability estimates. Of course, you need to have experience with the data you put in. You may have heard the old saying, "Garbage in. Garbage out." That is true when you are creating an oddsline with fundamental handicapping data. What comes out in the end is a function of what goes in in the beginning.

Read as many books on handicapping as you can. I like all of the books by James Quinn. William Quirin is very solid. Dick Mitchell, Mark Cramer, Bill Ziemba (Dr. Z) are all good. "Methods and Maxims of Pittsburgh Phil" is a classic. Books by Tom Brohammer, Howard Sartin, Andrew Beyer, Charles Carroll, and Cary Fotias are all excellent. Steve Roman's book used to be available for free as a pdf download. It's a terrific book on breeding and Dosage Theory.

A lot of people recommend Barry Meadow's book. I have tried reading it, but found it to be pretty dry. I prefer Dick Mitchell's writing style. However, Meadow's book gets mentioned a lot, so it probably appeals to others on some level that I can't appreciate.

There are other books that people here on PA like, but those are the ones I found most useful.

I just realized, I have met or seen in person all of those individuals except for Pittsburgh Phil and Bill Quirin. The reason I have met all those authors or listened to them speak is probably because I can relate to their books. I suppose I did not feel the need to reach out to the authors of the books I read that I didn't like.
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Old 07-16-2018, 04:44 PM   #34
BCOURTNEY
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A 4/1 horse on the tote board can be converted into the public's subjective probability of winning by removing the effects of the takeout.

P(pub)= (1-t)/(odds+1)

so if takeout is 16% then P(pub)= 0.84/5 =16.8%

If you believe its real chance of winning is 2/1 the the calculation of the probability does not involve take out (it will win one in three times) therefore P(your)= 33%

In this particular instance the whole line is probably out of whack due to a false favourite or something, or you have privileged information hidden from the public.

In the long term you would have to compare your odds with the public odds over the same selections to see if you really do have an edge. A good method would be to compute the Brier Score or Brier Skill Score.

http://www.statisticshowto.com/brier-score/
A Brier score is an affine transform of the quadratic scoring rule. There are also logarithmic and spherical scoring rules as well. The Brier score has some shortcomings should be used cautiously with respect to very rare (or frequent) event data.

Last edited by BCOURTNEY; 07-16-2018 at 04:46 PM.
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