Quote:
|
Originally Posted by Pell Mell
Help me to understand impact values, something I had never heard of until joining this forum. Evidently I have been using IV without knowing it for years or maybe I just play an angle. Tell me an approximate IV for my process.
I use the Bris custom card feature and scan an average of 50 or so races per day. I look for a particular factor which takes about 10 seconds per race. Out of 50 races which would be an average of 400 or so horses I may find 2 horses with said factor. Many days there are none and some days there are 4 or 5 so I don't know the actual average but I'm guessing at 2 per day. At the end of a month there may be 40-60 plays and these average 25% or more winners at an average mutual of 10/1. So what would be the IV of my angle?  |
From "The Handicappers Condition Book" by James Quinn pg 18, "The probability of winning equals simply the percentage of winners having a characteristic divided by the percentage of starters having the characteristic."
So in your case (assuming each race you are talking about only has 1 horse with your factor) with 50 races with 8 horses in the field per race (my guess) that gives you 50 horses with your factor and 400 horses total. So 50 divided by 400 equals 12.5% of starters have that factor. If your horse wins 25% of the time then 25 divided by 12.5 equals 2 or an Impact Value of 2 which is 100% more than would be expected. ( A value of 1 would mean that the factor is not significant either way. If you had Aunt Millie randomly guess the winner by picking just names she liked she would probably have been correct between 12 and 13% of the time. A factor can produce a negative expectation also for example (from the book) 1st time starters over all lose more than would be expected from their percentage of starters.
You sound like you are on to something good but check the link to Gordon Pine's article, it goes more in depth and confuses me a bit!!!
