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  #21  
Old 30th March 2015, 11:59 PM
walkermac walkermac is offline
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NRL Round 4 Review

Quote:
Originally Posted by walkermac

Tips:
South Sydney Rabbitohs
Canterbury-Bankstown Bulldogs
Newcastle Knights
Cronulla-Sutherland Sharks
St. George Illawarra Dragons
New Zealand Warriors
Sydney Roosters
Melbourne Storm

This round was 4/8, overall tipping is 20/32 (62.5%)


Quote:
Originally Posted by walkermac
"Value Bets" (not recommended for investment)
Parramatta WIN @ $3.30
Wests Tigers WIN @ $3.40
Gold Coast WIN @ $2.65
St George-Illawarra WIN @ $2.30

Canberra WIN @ $5.50

Bets were at $20.80

This Week
Out: $104
In: $171.60
65%POT

Overall
Out: $396.24
In: $505.09
27.5%POT

New Bank: $1108.85 (stakes for next round: $22.15)

Line S/R: 2/2 (100%)
H2H S/R: 8/17 (47.1%)

There may be a $ cut-off point for H2H bets that is becoming clearer. Only two of the eights successes were at greater odds than $2.80 (a narrow 16-14 victory paying $3.10, and the mostly unexpected Rabbits-Eels result of last week). As for the failing bets, 7 of the 9 were at odds of $2.95 or greater (a 19-18 result was $2.60, and an abysmal Dragons outfit went down 22-4 whilst offering $2.50). Though it's far too small a sample size to draw many conclusions from, it's something worth monitoring.


Quote:
Originally Posted by walkermac
The method is very much making selections on value rather than likelihood. Canberra, for example, is thought to get beaten by 24 points, but it contends the odds should be around the $3 mark. St George-Illawarra is the only pick to feature as both a Value Bet and a winner, so it's the only one I'd have any belief in (using this as a sub-selection method it's 6 successes from 9, thus far - and 2 of those failures were by only 1-2 points).

Now 7 successes from 10 for the subselection method. Quite a deal higher than the H2H S/R above.

Quote:
Originally Posted by walkermac
The bookmaker's line is the same as determined by the formula above (and the odds are lower than the total offered implies) for all games this round bar Sydney Roosters vs Canberra Raiders. In this case the calculated minimum margin is 17.4. Roosters -16.5 is currently paying $2.05 (Woohoo! Roosters -17.5 is greater still: $2.10).

Success here also: Roosters won by 28. Perhaps Centrebet lessens the margin it "should" be to try and attract bets for big underdogs...?
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  #22  
Old 2nd April 2015, 04:49 PM
walkermac walkermac is offline
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NRL Round 5

Using the "original" method (there's a chance of a version taking into account team strength and rugby league points distribution, later on).

Tips:
South Sydney Rabbitohs
Brisbane Broncos
Manly-Warringah Sea Eagles
Newcastle Knights
Sydney Roosters
Parramatta Eels
Melbourne Storm
Penrith Panthers

"Value" Bets (bets are $22.15):
St George Illawarra Dragons WIN @ $2.95
Cronulla-Sutherland Sharks WIN @ $5.15
New Zealand Warriors WIN @ $2.95
North Queensland Cowboys WIN @ $2.45

In previous posts I noted the increased success of these H2H bets when they were also tipped to win, or at odds < $2.95. By those measures, only North Queensland Cowboys @ $2.45 qualifies this week.

Gold Coast Titans were very close; if they drift out from their current $2.40 quote at all, they'd qualify as a value bet.

Lastly, checking what the line "should" be by that formula, no luck:
Newcastle -7.5 is paying $1.96
Roosters -15.5 is paying $1.99

They were the only options close to paying the minimum of $2.01 that Centrebet reckons you need to turn a profit (taking into account their starting prices and game total).
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  #23  
Old 5th April 2015, 01:30 PM
walkermac walkermac is offline
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The St George Illawarra H2H Value bet was successful last night. It was right on the divide where the picks seem to (at this early stage) either predominately lose or fail.

My means of selecting a bet as good value seems a little wanting. 'Til this point it's been: "Are Centrebet paying at least 15% more than I think they should?". What it doesn't take into account is the likelihood of the event actually occuring (in my estimation).

I was fiddling about with a Kelly Strategy Calculator and noted the output:

Code:
Results •The odds are in your favor, but read the following carefully: •According to the Kelly criterion your optimal bet is about 2.88% of your capital, or $33.11. •On 22.3% of similar occasions, you would expect to gain $132.44 in addition to your stake of $33.11 being returned. •But on those occasions when you lose, you will lose your stake of $33.11. •Your fortune will grow, on average, by about 0.16% on each bet. •Bets have been rounded down to the nearest multiple of $0.01. •If you do not bet exactly $33.11, you should bet less than $33.11. •The outcome of this bet is assumed to have no relationship to any other bet you make. •The Kelly criterion is maximally aggressive — it seeks to increase capital at the maximum rate possible. Professional gamblers typically take a less aggressive approach, and generally won't bet more than about 2.5% of their bankroll on any wager. In this case that would be $28.80. •A common strategy (see discussion below) is to wager half the Kelly amount, which in this case would be $16.55. •If your estimated probability of 22.3% is too high, you will bet too much and lose over time. Make sure you are using a conservative (low) estimate.

This was in regard to the head-to-head market for Cronulla winning this afternoon's match. Centrebet are paying $5; by my estimates they should be at $4.02 (I knocked a 10% discount off this figure to use a conservative estimate, as recommended).

The highlighted line is the interesting one. It seems to be a far better indicator of a value bet than purely assessing the $-value vs probability. In this instance, 24% better odds on offer (sounds good) vs a 0.16% bank increase (doesn't seem worth the risk).

So I had a fiddle about with other markets on offer and came up with a couple of bets that gave a greater bank increase (again, presuming my modelling is correct - then using a conservative estimate of that):

Cronulla to score >13.5
My odds = $1.40, Cb odds = $1.90
•Your fortune will grow, on average, by about 2.78% on each bet.

Either team wins < 12.5
My odds = $1.71, Cb odds = $2.20.
Your fortune will grow, on average, by about 1.02% on each bet.

The precentage figure refers to using FULL kelly staking and you likely wouldn't get the same returns using different staking, but it seems a reasonable indicator. What's a good % to aim for? I'm not sure, but I suspect anything >1% is awesome, despite how paltry it sounds. I might also be overly conservative with my 10% discount (for NZL below, the difference with/without discounting is 2.92% vs 1.25% growth).


For the other "value bets" remaining in this round:

New Zealand Warriors
My odds = $2.17, Cb odds = $2.95
•Your fortune will grow, on average, by about 1.25% on each bet.

North Queensland Cowboys
My odds = $2.06, Cb odds = $2.45
•Your fortune will grow, on average, by about 0.17% on each bet.

(Parramatta Eels-Wests Tigers is $1.84-$2.19 by my estimation and $1.80-$2.02 per Centrebet. Hence, neither team is a value bet - by either measure).
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  #24  
Old 7th April 2015, 01:37 AM
walkermac walkermac is offline
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NRL Round 5 review
Quote:
Originally Posted by walkermac
Tips:
South Sydney Rabbitohs
Brisbane Broncos

Manly-Warringah Sea Eagles
Newcastle Knights
Sydney Roosters
Parramatta Eels
Melbourne Storm
Penrith Panthers


This round was 2/8, overall tipping is 22/40 (55%)


Quote:
Originally Posted by walkermac
"Value" Bets:
St George Illawarra Dragons WIN @ $2.95
Cronulla-Sutherland Sharks WIN @ $5.15

New Zealand Warriors WIN @ $2.95
North Queensland Cowboys WIN @ $2.45

Bets were at $22.15

This Week
Out: $88.60
In: $233.68
163.8%POT

Overall
Out: $484.84
In: $738.77
52.4%POT

New Bank: $1253.93 (stakes for next round: $25.05)

Line S/R: 2/2 (100%)
H2H S/R: 11/21 (52.4%)


Quote:
Originally Posted by walkermac
In previous posts I noted the increased success of these H2H bets when they were also tipped to win, or at odds < $2.95. By those measures, only North Queensland Cowboys @ $2.45 qualifies this week.

It won. <$2.95 Sub-selection method is 7/9. (The other sub-selection method being monitored - i.e. also tipped to win - had no qualifiers this week; though it stands at 7/10).


Quote:
Originally Posted by walkermac
So I had a fiddle about with other markets on offer and came up with a couple of bets that gave a greater bank increase (again, presuming my modelling is correct - then using a conservative estimate of that):

Cronulla to score >13.5
My odds = $1.40, Cb odds = $1.90
•Your fortune will grow, on average, by about 2.78% on each bet.

Either team wins < 12.5
My odds = $1.71, Cb odds = $2.20.
Your fortune will grow, on average, by about 1.02% on each bet.

Both of these bets were successful. There were a couple more throughout the weekend that were also above that 1% mark and they won slightly more often than not.

The method I was working towards is more or less complete now. There are still some tweaks needed:
  • It's a pain in the rear checking the bookmaker's prices for each market manually
  • I need a means to record the markets and my own prices to examine what % (as above) I should aim for/to determine accuracy of my model
  • More results data! I've got around 10000 matches to better model point-scoring distributions; I'd like more. The problem I have is: gameplay has changed over the decades in NRL, so you have to look at other sources. I've had to borrow from other comps; how accurately do they mimic NRL results? Toyota Cup (the U20 youth competition) is mocked for having high-scoring matches. European Super League clubs aren't as evenly matched across the competition.
  • More fantasy points data! I track this as a means to determine team strength from week-to-week. I only have it (points earnt & teams played for) for seasons 2013-2015. I'd like to look at more historical predictions that take this into account. There appears to be different standard deviations of the prediction error between home and away sides - it is likely even more team-specific than I'm presently able to confidently determine.
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  #25  
Old 7th April 2015, 09:47 AM
evajb001 evajb001 is offline
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walkermac,

Looks like your doing really well with your modelling, that is an absolute cracking week on the value bets can't ask for much more than that. One suggestion/question I have is have you looked at using other bookmakers besides centrebet? I use 4 bookmakers for my sports betting and 2 in particular are much better than centrebet for H2H odds and line odds but don't offer the more exotic markets that you've alluded to either.

For instance even though I had a poor round for my AFL rating system betting, all my line odds were $2 or better and often 2-4 points better then the worst line available out of the 4 bookies. It can be a bit of extra stuffing around but say centrebet's line is (for an AFL game) -16.5 @ $1.91 and you can achieve -14.5 @ $2.00 elsewhere it could make a significant difference over the long term.

Anyhow just an idea, definitely watching your thread with great interest as I much prefer the build your own model approach then following any form of tips etc. If your interested in what bookies I can post my email address as I'm not sure whether mods are happy with bookie names being posted.

Josh
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  #26  
Old 7th April 2015, 01:18 PM
walkermac walkermac is offline
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Quote:
Originally Posted by evajb001
Looks like your doing really well with your modelling, that is an absolute cracking week on the value bets can't ask for much more than that.

To be honest, I think it's over-achieving Either the bookies are a bit frazzled being early in the season; I've been underestimating my own prices; else it's just plain luck. ...likely the last.

Quote:
Originally Posted by evajb001
One suggestion/question I have is have you looked at using other bookmakers besides centrebet?

Not really. But I do hasten to add that you're totally correct. I'm a terrible gambler 'cause I hate losing. I got some free money from Centrebet - and have yet to replenish - so have always just stuck with them! The free money worked in one respect: I had zero interest in sports betting or horse racing until I got it. I subsequently discovered that it hits a sweet spot of my lapsed mathematics and lapsed computer science skills, along with my love for free stuff (presuming I'd ever succeed).

Now that it seems that I may be developing some kind of ability, further betting accounts is something I should definitely consider. ...I just have to get over actually withdrawing cash from my bank account :S

Quote:
Originally Posted by evajb001
Anyhow just an idea, definitely watching your thread with great interest as I much prefer the build your own model approach then following any form of tips etc. If your interested in what bookies I can post my email address as I'm not sure whether mods are happy with bookie names being posted.


Cheers, Josh. I appreciate the interest. When I first started lurking here there were a number of contributors I especially enjoyed reading. Given my academic background and that I barely knew which end of a horse the food goes in; it was posts from guys like yourself, UselessBettor, Rinconpaul and (historically) woof43 that indicated there was a chance for someone like me to make a go of it!

(not to imply that any of you similarly have no idea regarding horses, just that I appreciated the intellectually rigorous approaches y'all took)
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  #27  
Old 7th April 2015, 02:04 PM
walkermac walkermac is offline
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Made a mistook in the Round 5 Summary. I marked Melbourne as an unsuccessful tip, but they actually won. Correct results are:

This round was 3/8, overall tipping is 23/40 (57.5%)
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  #28  
Old 10th April 2015, 05:30 PM
walkermac walkermac is offline
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NRL Round 6

Was a bit slack leading into this round. I put off doing any work on it 'til later in the week, and then had a number of unplanned activities that didn't allow for it.

The good news is that I've sourced fantasy points data from another couple of years previous, which will allow me to perform some tweaks with more confidence, in the near-future. Even with only the past 2 year's worth of fantasy points (which I'm using to monitor team strength, from round-to-round) it's clear that it provides a nearly 5% boost to tipping results. As a consequence, tips and value bets will take this into account (unlike previous weeks). I'll still be using the "original" means of creating prices and determining value bets though - not using a Monte Carlo simulation.

Tips:
Newcastle Knights
Sydney Roosters
Parramatta Eels
Wests Tigers
Penrith Panthers
Melbourne Storm
Canterbury-Bankstown Bulldogs
South Sydney Rabbitohs

"Value" Bets (bets are $25.05):
Gold Coast Titans WIN @ $3.10
Wests Tigers WIN @ $2.80


Wests Tigers qualify both of the sub-selection methods I'm monitoring: "price under $2.90" (7/9) and "tipped to win" (7/10) ...making them a "Super Value Bet"?
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  #29  
Old 15th April 2015, 03:41 PM
walkermac walkermac is offline
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NRL Round 6 Review

Lost my internet connection for most of the past week. Lucky I was knocked out of the Tipping Comp the Saturday previous... With a few less distractions I was able to put in some work; further posts to come.

Quote:
Originally Posted by walkermac
Tips:
Newcastle Knights
Sydney Roosters
Parramatta Eels
Wests Tigers
Penrith Panthers
Melbourne Storm

Canterbury-Bankstown Bulldogs
South Sydney Rabbitohs



A 2/8 tipping performance gives a running season total of: 25/48 (52.1%).

I've been doing some backtesting and - for some reason or other - this season it's been going considerably worse at picking winners. There haven't been great changes to the rules (despite talking of "speeding up the ruck" and all this may entail; to my eye it's made little difference) and squad changes are staggered (rather than all happening at one time every 3 or 4 years); so I'm not sure of the cause. Statistical abberration or long overdue correction?

Quote:
Originally Posted by walkermac
Gold Coast Titans WIN @ $3.10
Wests Tigers WIN @ $2.80

Bets were at $25.05

This Week
Out: $50.10
In: $77.66
55%POT

Overall
Out: $534.94
In: $816.43
52.6%POT

New Bank: $1281.49 (stakes for next round: $25.60)

Line S/R: 2/2 (100%)
H2H S/R: 12/23 (52.2%)


Quote:
Originally Posted by walkermac
Wests Tigers qualify both of the sub-selection methods I'm monitoring: "price under $2.90" (7/9) and "tipped to win" (7/10) ...making them a "Super Value Bet"?

Didn't catch the game, but apparently the Tiges weren't far off. Perhaps they may have shaded the Warriors on any other day but the occasion of Manu Vatuvei's 200th. Running results are 7/10 and 7/11, respectively.
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  #30  
Old 15th April 2015, 11:30 PM
walkermac walkermac is offline
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I developed an automated testing system which would allow me to perform tweaks to settings and "quickly" assess the results (it takes around 45 minutes to run).

One of the things I discovered (and expected to find) was that the method doesn't perform as well during the early rounds of the season:

Rounds: 1-9 % of correct tips: 60.9%
Rounds: 10-18 % of correct tips: 62.4%
Rounds: 19-26 % of correct tips: 66.7%


The tweaking was to determine what league-wide figures to use to better account for home-away-neutral matches in making a prediction. I used the set of data comprising the full seasons of 2013 and 2014. Results were a 64.1% rate in correctly selecting the match winner.

How does it compare on another set of data? 2012 results: 63%.

Which appears encouraging. What is not-so-encouraging is the performance so far in 2015 (at the completion of round 5): 50%. ...which is about 9% lower than in past year's (over the same number of rounds). Still, that's only 4-5 games down out of 48.


I can also determine team-specific figures for home-away ad-disadvantage; but I was a little torn on how/whether to use this data. Given that most NRL teams are within a bus ride from each other, results seem more due to innate team performance (which would vary from season to season as the player roster does) rather than privation (due to travel distance/time zone change, for example).

In a hypothetical match between the North Queensland Cowboys (home) vs the Sydney City Roosters (away), it would seem to make more sense to account for the historic performance of every away team in Townsville, rather than the away performance of the Roosters (over some indeterminate period of time).

That makes a modicum of sense for a geographically isolated team such as the Cowboys, but if it's a Sydney-based team, there's surely a difference between an Away team from down the road vs an Away team from across the Tasman!

As per usual, someone's already studied this aspect - in greater detail than I'm capable of, over a wider array of sports - and determined that travel effects on results is minimal ("Travel and the Home Advantage in Professional Sports" by Smith, et al). They don't really explain the standard observed home advantage, aside from speculating that it's due to a "socially constructed reality" courtesy of players/coaches/media/officials. And that reality is presumably league-wide.
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