Is it really true that the more rules you have in the system the less effective it is in the longer term?

I understand the concept of back filtering but still not quite sure that a system with more rules has more probabilty of failing.

If you generate a system with 3-5 rules with 40,000 selections - 25%SR - 10,000 winners at avg of $5.00 thats a POT of 20% ($10,000 - profit). Just an example.

If you restricted that to 15 rules and come up with only 2000 selections for 40% strike rate for 800 winners at avg of $5.00 you have a profit of $2000.

Betting level stakes would seem to continue with the 3-5 rules at Profit is more, but with confidence in a higher strike rate you can use a larger stake of your bank like 5%, instead of 1-2%.

Back to my original point, by filtering more rules why does everyone say its setup to fail? Is confidence increased by not on the amount of horse races bet on or is it by the number of meetings tested and eliminated when they don't fit the criteria?

Just interested to know others thoughts?

I'll give it a stab and try to give a reason.

Backfitting is a problem when the rules you add are not aded for a logical reason. The more rules you have the more likely that you are backfitting some of those rules.

The other reason is that usully the more rules you add to the system, the more you restrict the result set. Less results mean less confidence.

I can find many systems that only have 2 rules that make 5% plus but I have to say that variance is huge in these systems. You go from -20% to +20% swings and the average punter couldn't handle them(me included). So I think adding a couple of extra rules to minimise the variance is acceptable.

The more rules you have the more it leads back to the selection becoming the fav and at best scenario favs lose 67 % of races.
Cheers
darky

There's a golden rule I have.
Unless you can properly explain the reason for the rule, leave it out.
That's why so many systems fail.

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If your original system has a 10% POt and you add another 5 rules, does that mean the your system will drop below the 10% POT. You have have to say no in theory.

I using a 2 step model. Using 3 rules as a base to get a 10-15% POT and adding extra filters.

I know in the end of the day, the horses that should have won only to be let down by the jockey or sweating/playing up at the barriers.

As few rules/filters as possible is best. I seldom use more than two or three with laying.

The problem with using alot is that they begin to overlap. The rules should be independent of each other.

__________________
Pixie

"It's worth remembering that profit isn't profit until it's spent off the racecourse." -- Crash

If you add the extra rules to tighten up the selection process or to specifically isolate the value runners then I don't see a problem. If it's obvious that your selections are disadvantaged in certain states/conditions and your strike rate and POT increases as a result then go for it.

The see systems as a set of rules constructed to either:

(a) Isolate undervalued runners in the market
(b) Isolate absolute good things that have many lengths on the opposition and will be able to sit 3 wide and still bolt in. As most know, these systems usually end up with very low action.

Whatever you do, keep monitoring the results so that you can justify when things go good or bad and tighten things up if it's appropriate.

The Schmile

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The Schmile

"I buy when other people are selling.”
― J. Paul Getty

General the more rules one has , the less likely history will repeat itself.

When running tests on systems...

One method is to run them in batches of 150

Some batches will show a profit & other batches may very well break even.

That way one gets a stronger idea if the plan has any legs or not.

Is also a strong idea to test the price range the winners came from also.
If profit came from say 1-2 outsiders , then the warning bells should be sounding because the system is less likely to repeat that result.

The term Back fitting is often used as a derogatory word to describe a system that was shoe horned into making a profit using a hundred rules over layed on past data .
In other words the data was massaged into profit by adding a hundred rules.
.
I believe seeing that future data is not available then that's all we have to work with.
The question we are then left with, is will these rules repeat themselves into the future.
Some do & some dont,
That's why it is suggested to run the rules over previously unseen data to see if it holds up..

Once we have a lot of races say over 4.5 years , its an idea to batch them into lots on 150 races & see how consistent it may be.
We have all seen systems that absolutely nail it over say a 3 month period , then fall in a hole - Very frustrating.



Here is an example.

Lay Plan
Lay bet all 2nd Favs priced 2.00-4.90 that have a win SR of 20-23% in races with 9+ runners.

What stands out here as possible back fitting, is the 20-23% win SR.

This may tell us the the percentages have been cherry picked ,to force that data into profit.
This may or may not repeat itself.
One would have to then run this against unseen data to see if it holds up.
It may indeed be a loop-hole based on punters over betting these commodities because of this popular percentage range punters & systems ,like to use in their rules.

Because there are only a few rules , there is a strong chance that the data may repeat itself.

That Lay Plan above, is currently showing...
+36% POT
80% SR

__________________
Cheers.

Nice post Bhagwan,

Completely agree.

The Schmile

__________________
The Schmile

"I buy when other people are selling.”
― J. Paul Getty

Couldn,t agree more.