Domain, EstStart, LaySelection, AvgOddsObtained, TourName, Players
WTA, 18/02/2011 15:30:00, Petra Martic, 1.71, Copa Colsanitas - Bogota, (Petra Martic v Laura Pous-Tio)
ATP, 19/02/2011 01:00:00, Andy Roddick, 1.41, Regions Morgan Keegan Championships - Memphis, (Andy Roddick v Lleyton Hewitt)
ATP, 18/02/2011 17:15:00, Sam Querrey, 2.28, Regions Morgan Keegan Championships - Memphis, (Sam Querrey v Mardy Fish)
WTA, 18/02/2011 15:30:00, Petra Martic, 1.71, Copa Colsanitas - Bogota, (Petra Martic v Laura Pous-Tio)
ATP, 19/02/2011 01:00:00, Andy Roddick, 1.41, Regions Morgan Keegan Championships - Memphis, (Andy Roddick v Lleyton Hewitt)
ATP, 18/02/2011 17:15:00, Sam Querrey, 2.28, Regions Morgan Keegan Championships - Memphis, (Sam Querrey v Mardy Fish)
Masquerade
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I don't have excel on this computer. But are you saying over 45 bets you're up £608 with ROI of 13%? Do you think the ROI is fair or are you running above/below your expectancy?
Yes that's correct. I would prefer to build up a bigger buffer as the inevitable losing runs will kick in soon enough but is always nice when you are only eating into the profit. Well it covers 6 losing bets for me, so not that great yet but I'm not complaining 
!
!I think I posted a few days back that I was expecting a ROI of around 10-20 percent (before commission should I add) so I am happy with this currently as is in higher end of expected scale. I'd be happy though with anything over 4% (after commission), it is hard work so hopefully will pay off.
Masquerade
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One interesting thing to do is flip a coin and compare your results to a coin flip over a sample of bets and see which performs better.
In my opinion, but happy to be proved wrong by yourself or a statistics boff, this is not comparable for 2 reasons:
1) I am staking the same liability per bet regardless of odds. The reason I do this is because I know over the long run my strength lies in laying the low odds shots i.e., 1.1 - 1.66 odds range. Ideally I would lay an amount equal to my expected edge, but I am not a Kelly advocate and don't feel I know my true edge down to an individual price.
2) A coin toss is a 50/50 chance. Whereas my odds are all over the place.
What I should do is add a column to my spreadsheet showing the expected profit/loss I would have given the probabilities of the odds taken. These could then be compared for more validity. Maybe I'll add something tonight.
BTW, you can get open office for free which I believe you should be able to open excel documents (or if you have got a hotmail account you could send the file to yourself as you can now view excel docs in hotmail).
Here is a post from another forum on this topic (posted by somebody called robert99) but the Archie technique I believe was founded by Steve Tilly, I am assuming this is correct and will see how it works out :
This might help:
Quote:
Originally Posted by Overlay
Can you just take the odds at face value in calculating expected winners? Don't you have to factor take and breakage into the calculations? For example, with a 17% take and dime breakage, wouldn't the expected percentage of winners for horses with odds of 4-1 be (1 - .17) / (4.00 + 1.05), or .164 (16.4%), rather than 20%?
In UK, you can bet to near zero takeout. Anywhere else, of course, you may need a shrinkage adjustment. If you don't want to make the adjustment you will be on the safe side for any conclusions though.
My post today got a bit messed up. Here is a corrected version:
"The mathematical formula we use in UK is based on the Chi Squared statistic
and is referred to as Archie. It tells you how likely your results are,
based upon chance. If you are OK with them having a 90% chance of being
based on skill/knowledge then you need less results/data than if you want to
have a 95% assurance. You can never get to 100%, however much data you have and by the time you had that data it would be long out of date and
erroneous.
The Archie test is done as follows:
selections × (winners - expected_winners)2
------------------------
expected_winners × (selections - expected_winners)
Expected winners - you need to know the final odds of every selected horse
to work out its best estimated chance. Add up all of the odds as follows:
If the horse started at 4/1 the chance is 1/(4+1) = 0.20 (20% chance) and so on. That horse would be 0.20 of an expected winner. You add up all those
expectations for each selection to give a total expected number of winners.
If for a test example, selections = 1400 and actual winners = 281
and your summed expectation was 249 winners, your Archie equation becomes:
1400 × (281 -249)2
-----------
249 × (1400 - 249)
= 1433600/286599 = 5.002
which gives an Archie Score of approximately 5
Check your Archie score against the Archie table :
Archie Archie Probability
0.3 0.5839
0.5 0.4795
1 0.3173
1.5 0.2207
2 0.1573
2.5 0.1138
3 0.0833
3.5 0.0614
4 0.0455
4.5 0.0339
5 0.0253 (example)
5.5 0.019
6 0.0143
6.5 0.0108
7 0.0082
7.5 0.0062
8 0.0047
8.5 0.0036
9 0.0027
9.5 0.0021
10 0.0016
10.5 0.0012
11 0.0009
11.5 0.0007
12 0.0005
So we look for Archie score = 5 which represents a probability of roughly
2.53% that your method of selecting those winners was just down to chance or fluke. So it is 97.47% probable that the method success was not just due to chance.
If you want more reassurance, you need a higher Archie score and more
samples."
This might help:
Quote:
Originally Posted by Overlay
Can you just take the odds at face value in calculating expected winners? Don't you have to factor take and breakage into the calculations? For example, with a 17% take and dime breakage, wouldn't the expected percentage of winners for horses with odds of 4-1 be (1 - .17) / (4.00 + 1.05), or .164 (16.4%), rather than 20%?
In UK, you can bet to near zero takeout. Anywhere else, of course, you may need a shrinkage adjustment. If you don't want to make the adjustment you will be on the safe side for any conclusions though.
My post today got a bit messed up. Here is a corrected version:
"The mathematical formula we use in UK is based on the Chi Squared statistic
and is referred to as Archie. It tells you how likely your results are,
based upon chance. If you are OK with them having a 90% chance of being
based on skill/knowledge then you need less results/data than if you want to
have a 95% assurance. You can never get to 100%, however much data you have and by the time you had that data it would be long out of date and
erroneous.
The Archie test is done as follows:
selections × (winners - expected_winners)2
------------------------
expected_winners × (selections - expected_winners)
Expected winners - you need to know the final odds of every selected horse
to work out its best estimated chance. Add up all of the odds as follows:
If the horse started at 4/1 the chance is 1/(4+1) = 0.20 (20% chance) and so on. That horse would be 0.20 of an expected winner. You add up all those
expectations for each selection to give a total expected number of winners.
If for a test example, selections = 1400 and actual winners = 281
and your summed expectation was 249 winners, your Archie equation becomes:
1400 × (281 -249)2
-----------
249 × (1400 - 249)
= 1433600/286599 = 5.002
which gives an Archie Score of approximately 5
Check your Archie score against the Archie table :
Archie Archie Probability
0.3 0.5839
0.5 0.4795
1 0.3173
1.5 0.2207
2 0.1573
2.5 0.1138
3 0.0833
3.5 0.0614
4 0.0455
4.5 0.0339
5 0.0253 (example)
5.5 0.019
6 0.0143
6.5 0.0108
7 0.0082
7.5 0.0062
8 0.0047
8.5 0.0036
9 0.0027
9.5 0.0021
10 0.0016
10.5 0.0012
11 0.0009
11.5 0.0007
12 0.0005
So we look for Archie score = 5 which represents a probability of roughly
2.53% that your method of selecting those winners was just down to chance or fluke. So it is 97.47% probable that the method success was not just due to chance.
If you want more reassurance, you need a higher Archie score and more
samples."
I have added this to my spreadsheet and can see that there is around a 19% chance (archie score = 1.75 therefore, (0.2207 + 0.1573) / 2 = .189) that my profit so far is due to chance (including the extra loss of my Roddick bet). I don't often do these statistical tests, I much prefer to get a big enough sample size for it to be almost conclusive in its own right. I would argue that this figure of 19% should be lower as I have not accounted for the overround loss I will generally get with my matched bets and the additional commission charge on the winners).
Oops I should NOT have wrote
"there is around a 19% chance that my profit so far is due to chance",
this is incorrect, I meant, there is a 19% chance that my tennis bets having an edge is down to chance (I can't say profit because my staking plan will have an influence!)
"there is around a 19% chance that my profit so far is due to chance",
this is incorrect, I meant, there is a 19% chance that my tennis bets having an edge is down to chance (I can't say profit because my staking plan will have an influence!)