Hi,

Can anyone help with a formula for converting rating figures to odds (such as Sportsman Zip or QldTAB ratings).

I was using - total all ratings and divide the individual by the total for a percentage which is easily converted to odds - where this seems to come undone is...
5 horses with ratings 100,80,80,80,80,80 for a total of 420, so horse 1 has 23.8% chance of winning.
Now add another 5 horses all rated at 80 each to the above and re-calculate horse 1 - we get horse 1 with 12% chance to win.

If the above #1 horse was Lohnro, the diffreence in winning percentage seems incorrect.

Play around with a points scale until you get something that seems OK for you. Eg. rating 100 = 100 points, rating 99 = 90 points, rating 98 = 79 points etc.

There's a detailed discussion about this topic on this very same page!

Typically you CANNOT just add rating points together.

You have to examine past results to produce a table converting ratings difference to relative chances - then add those.

A rating of 80 (i.e. 20 points worse than 100) is typically very bad. Yet your assumption is that an 80 horse will beat a 100 horse 80 times out of 180 i.e. ~43%.

Ridiculous!

Check out a computer program called Bet Master from Inracing, it is a dutch betting program that allows you to also create your own market using wt ratings or Zip form ratings .

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Cheers.

Hi everyone,

Wondering if anyone knows where to get an english copy of Bet Master.

[ This Message was edited by: puntz on 2004-06-07 21:17 ]

Bill,

I can help you with something for Sportsman Zipform ratings...

1. Take the base Zipform Rating;
2. Add a point if the horse's speed is marked 'H';
3. Add a further point if the horse marked 'H' has drawn a barrier inside the 80% band (i.e. in a 10 horse field barriers 1 to 8). Note this applies to races with fields greater than 8 only;
4. Add a point if the horse is ridden by a jockey in the Top 5 of the premiership (by strike rate);
5. Deduct a point if the horse is weighted above the top Zipform rated horse.

Now you have an adjusted points table for the race, give the top rated horse a score of 100. Then give the next score 92, the next 84 and so on in multiples of 8.

Note, no horse can score less than 4. So, if there are more than 13 points difference between the top rater and the bottom raters, after the 13th, give each horse 4.

The as you suggested add these scores up and then divide each individual score to get a percentage chance for each horse in the race.

From here it is up to you as to what market percentage you wish to frame your prices.

Hope you find this of value.


Cheers,
Luckyboy


[ This Message was edited by: on 2004-05-20 08:02 ]

This is the method I use. It's similar to what Don Scott used to do. It's really for using on weight ratings with 1/2 kg differences, but you should still be able to use it on Unitab and Zipform ratings. I hope so anyway.

Firstly, you convert your ratings to a score out of 100 using this table:

Top rated horse = 100 points
0.5 kgs behind = 85 points
1.0 kgs behind = 70 points
1.5 kgs behind = 60 points
2.0 kgs behind = 50 points
2.5 kgs behind = 44 points
3.0 kgs behind = 38 points
3.5 kgs behind = 33 points
4.0 kgs behind = 28 points
4.5 kgs behind = 24 points
5.0 kgs behind = 20 points
5.5 kgs behind = 17 points
6.0 kgs behind = 14 points
6.5 kgs behind = 12 points
7.0 kgs behind = 10 points
7.5 kgs behind = 8 points
8.0 kgs behind = 6 points
8.5 kgs behind = 4 points
9.0 kgs behind = 3 points
9.5 kgs behind = 2 points
10.0 kgs behind = 1 point
10.5+ kgs behind = 0 points

Then you simply add up the scores of all the horses in the race to get a total. To get each horse's price you simply divide the total by their score.

Here's an example race:
No.1 - Rtg 59 = 100 points
No.2 - Rtg 57 = 50 points
No.3 - Rtg 56 = 38 points
No.4 - Rtg 54 = 20 points
No.5 - Rtg 53 = 14 points
No.6 - Rtg 56 = 38 points

The total of all the scores is 260, so you simply divide 260 by all the horses' scores, do a little rounding up or down and you get the following approximate dividends:

No.1 - $2.60
No.2 - $5.20
No.3 - $6.80
No.4 - $13.00
No.5 - $18.60
No.6 - $6.80

That is of course a 100% market. If you want to get a market which more accurately compares with TAB prices, you should actually multiply that figure of 260 by .85 and then divide it by the horses scores.

Anyway, I hope all that has been of some help.



[ This Message was edited by: sportznut on 2004-05-20 11:00 ]

Pure gold Sportznut!

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Sportz,

That is very interesting. Is there any rationale behind the wide points spread for top weighted horses versus the compressed nature of the lower weighted horses?


Cheers,
Luckyboy