Why You Should Use Impact Values
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by: John Blair
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If you are a regular at the Race Advisor or other betting forums then you may have heard of the term impact value before. It is unknown amongst the majority of the betting public and often its value is not understood.
However for those who understand the power of impact values a complete knew way of analysing factors in sports betting will open up for you.
This technique can be applied to any sports where you have ratings or factors.
Let me explain how you calculate an impact value first and then I will explain why they are so useful.
To calculate an impact value you are going to need some historical data for whatever factor you want to analyse. A factor does not have to be a figure which has been created, like a speed rating, but can also be a certain set of conditions. My examples will be from horse racing but this can be applied to any sport.
By a set of conditions I mean that you may consider...
Horses who won last time out at the same course
or
Horses who didn't win but finished within 3 lengths of the winner in their last 3 races
To calculate the impact value we use the sum...
% of winners with factor / % runners with factor
For our first example we would take some historical data, e.g. the last 6 months, and from that we would find all the horses that won last time out at the same course. If we have 10000 runners in our historical data, 1000 won last time out at the same course and of these 250 won then we know that...
250 winners from 1000 with our factor = 25% or 0.25
1000 runners with our factor from 10000 runners in the data = 10% or 0.10
We can now put these figures into our sum...
0.25 (% of winners with factor) / 0.10 (% of runners with factor) = An Impact Value of 2.5
That's great but what does it mean?
This means that these runners win 2.5 times more than they should!
Don't mistake that for meaning that these selections will make a profit. It doesn't. But it does mean that these runners are going to win 2.5 times more than you would expect them to based on random chance.
If you find this out for a few different horses then you can begin to find runners which are hugely more likely to win than they should.
Next I am going to show you how you can change the calculations of the impact value to make it an even stronger measurement.
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