Hey systems punters - can one of you answer a question for me? It's been bugging me for quite some time. How do you work out the probability of a given run of outs of a system based on it's strike rate, and therefore what is a reasonable bank to have to support any potential run of outs for a given method?

For example, say you've got a method with a 20% strike rate. What is the % stake of your bank you should use (level stakes) whereby any reasonable run of outs can be endured? And what runs of outs can one expect with a 20% strike rate? Or 40%? Or 10%?

What's the calculation punters?!

Your help appreciated.
Duritz

The answer is not as simple as stating with a 20% strike-rate there is an expectation of X being the longest run of outs. It really depends on the number 'events' that the 20% strike-rate is being tested on. For example, there is a 56% expectation of a longest run of outs in any 100 'events' with a 20% strike-rate, but over 1000 'events' there is a 52% expectation of a longest run of outs of 25. Over 10,000 there is a 55% expectation of a run of outs of 35.

Of course there would be greater expectations of runs of outs of lesser amounts.

Have a look at the thread PROPUNTERS.
I believe Neil has something there on losing runs.
Cheers.
darky.

If you are losing 50%, your chance of losing 10 in a row is:
1/(.5 * .5 * .5 * .5 * .5 * .5 * .5 * .5 * .5 * .5) = 1 in 1024.

If you are winning 20% and losing 80%, your chances of losing 10 in a row is:
1/(.8 * .8 * .8 * .8 * .8 * .8 * .8 * .8 * .8 * .8) = 1 in 9.3

You cannot workout a longest losing run, because there is no such thing. Whilst there is a chance of losing the next race, the figure is infinate.

And how meaningful is this "Longest run of outs" anyway? If you calculate your maximum run of losses is likely to be 20 and you give yourself a safety net by betting a twenty-fifth of your bank - what happens when you have a run of 15 losses a win or two and another 15 losses? Your bank is still going to be caput.
When I computer model my systems against past data I record the high point of my bank and the worst following low point and work out the equivalent number of bets I lost from my peak to my trough. I have no idea how you would work this out from a percentage strike rate though.

KV

mate with 20% strike rate i would suggest betting flat stake 1% of bank.