You can tweak something like this a lot of different ways.
In the end, no matter what tweaks are made -- hopefully, what you end up with is a number that measures performance vs. expected performance.
In his book
Precision, on page 80, CX Wong wrote about a stat called Cumulative Probability or F(x) and presented a formula for calculating it.
It takes a little programming to calculate it, but I've found that Cumulative Probability or F(x) does a decent job of measuring performance vs. expected performance in a statistically valid way. (All of the values generated end up being between 0 and 1 and any value >= 0.50 suggests the rider, trainer, sire, what have you, etc. outperformed expectations.)
Imo, the way to get bang for your buck or separation between yourself and the other players who you are competing against in the pools with a stat like this doesn't necessarily come from the tweaks, although doing that can provide a degree of separation -- but rather from applying a stat like this in a conceptually unique way vs. the way the other players you are competing against in the pools are applying it.
For example, in the DRF podcast for his new book
Betting with an Edge, Mike Maloney talked about the value of knowing whether or not a rider likes to be inside or outside.
I'm not saying that knowing an inside rider from an outside rider is the be all end all of things (it's not.) But the database testing I've done suggests that knowing that and measuring performance produces better results than ignoring that and measuring performance for rider alone.
Imo, if you can give a stat like this some thought, and get creative about what is or isn't reflected in the odds:
And from there measure performance for rider, trainer, sire, what have you, etc, vs. expected performance
given the situation...
I've found at that point you are more likely to actually HAVE something.
I hope I managed to type most of that out in a way that makes sense.
-jp
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