In sports betting there’s a genuine buzz that comes from “getting it right” — especially when you correctly predict something against the odds. This often manifests itself in a winning gambler’s swagger.
But before you start “making it rain“ in front of your pals, you should ask yourself: have I been lucky, or unlucky? Is my current strike rate likely to continue? What does the future hold?
If you’re placing a lot of bets then you ought to stop and check whether or not your strike rate is realistic. I’ll show you how.
Striking It Lucky?
One of the main problems with sports betting is that there’s no publicly available frame of reference to show you whether your observed results are reasonable.
You might be winning — but you’ve simply been fortunate. Or you could be losing despite the fact you’ve consistently bet on value. It’s not as if the Bookmakers give you feedback and tell you “this was good value” or “this definitely wasn’t a value bet”. It’s down to you to determine whether or not your bets were smart ones.
Professional Betting Analytics Software
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A Simple (Free) Approach
If you’re just starting out and have no intentions of investing in analytics software, the best advice I can give is to record each of your odds and results, and to start ignoring what you’ve made or lost for the time begin. That’s not immediately important.
Understandably, that might sound unusual.
But imagine the bulk of your winnings came from one or two long-shots, at say 30/1. Or the bulk of your losses came from bets where you lost large stakes, and only managed to win on smaller ones. These cases disguise whether your bets were truly good or bad value.
You need to make a fair assessment of your performance. I’ll show you how to do this by referring to a sample set of ‘Mug Bets‘, where I placed an equal stake on every Premier League game within a season.
The Real Chance Of Striking A Win
Some bettors will formulate their own probabilities for sporting outcomes and use them as the basis for selecting bets. Those percentages can be directly translated to odds, as I’ve shown in my post: What’s A Value Bet?
Whatever you use as your benchmark of accuracy, It’s important to note that:
- Bookmakers tend form odds that overestimate the chance of an event occurring (i.e. the odds are low).
- Betting exchanges tend to form accurate estimates for an event occurring (i.e the odds are fair). These are said to be “sharp”.
Therefore, if you have nothing else to go by, the Betfair odds are a good estimator of the fair price (in liquid markets, especially).
The Average Odds
To achieve more insight from the sample of bets, work out the (mean) average odds taken. Simply add up all of the (decimal) odds together and divide by the number of bets you placed.
In the case of my Mug Bets, as of the time of writing, I’ve placed :
- Bets: 173
- Total Odds: 689.49
Therefore, the average odds I bet on were 689.49/173, which is 3.99.
Now I can work out what the “implied” chance (%) of winning those bets was by calculating 1/3.99, which gives 0.25, or 25%.
So my bets, up until this point, had a 25% (or “1 in 4”) average chance of winning, according to the odds I took. Simple so far.
How Have my Bets Performed?
To assess my performance I need to count up how many of the sample bets won. Again, I’ll continue to ignore the profit entirely.
In my sample I’ve had:
- Bets: 173
- Bets won: 70
Therefore, 70/173 = 0.40 = 40% of the bets won.
Now we have a comparison:
- Actual winners: 40%
- Implied chance of winners (based on Betfair odds): 25%
40% is what we refer to as the “strike rate”. Therefore, so far I’m winning +15% more bets than the market predicted.
The question is, how realistic is that? Will this strategy be profitable going forward? Do I know something more than the market?
Assessing The Observed Strike Rate
My observed 15% over the expected win rate is a bit on the high side. Usually the strike rate will somewhat reflect what the Betfair exchange odds imply, tending towards a 0% difference.
But there’s two major considerations to account for here:
With the average odds implying a 25% chance of winning, it’s not an infeasible result. Swings — a.k.a the “variance” — is increased by using high odds. If I’d used lower odds, there would be less chance of such a ‘deviation’ occurring.
So if, for example, my average odds implied a 50% chance of winning each bet (2.0 decimal odds), then I would expect more predictability in the results. I would expect the difference between my real strike rate and the implied chance to be much smaller.
2. Sample Size
The size of the sample is vitally important for gaining certainty in results.
At this point I can’t be sure whether I’ve got an ‘edge’ in my strategy or not. I could’ve been lucky. The reality is that 173 bets simply isn’t a big enough data set to tell. The more data, the better.
Update: by the end of my experiment, my betting results evened out and I broke even with a 0.00% ROI. Therefore my strategy did not have an edge after all. Early results over-performed.
Standard Deviation — a Step Further
The above steps are only for a rough guideline. To fully determine whether or not you have an edge in your bets, then you need a big sample and a proper metric to determine whether your results are truly “fair”. This is where the standard deviation comes in.
The standard deviation is a number used to tell how measurements for a group are spread out from the average (mean), or expected value. A low standard deviation means that most of the numbers are very close to the average. A high standard deviation means that the numbers are spread out.
For sports betting, you compare the expected value (the implied odds) against the measurements (the actual results). What you hope for is a fairly low standard deviation, but with a positive edge in your bets within the region of 1-10%. I would avoid getting too excited if you observed better results than that — because betting markets are intelligent and very tough to crack. Your margins won’t be astronomical.
I’m not a maths teacher, so I won’t show you step-by-step instructions of how to work out the standard deviation. I don’t think you’d want to read it either. There’s plenty of tutorials and calculators online. It’s not unique to sports betting by any means.
The Most Important Point About Strike Rates
Most importantly, in any long-term betting strategy, you need to remember that strike rate itself is meaningless unless the odds represent value.
Suppose you only ever bet on extremely strong favourites with average odds of 1.1. In this situation your strike rate will be high — because these odds have an implied 90.9% chance of winning. But ultimately there’s no gain if those odds weren’t high enough to generate a positive ROI over the long-term.
Similarly, betting on only high odds — let’s say 200.0 — would be certain to produce an extremely low strike rate given its implied 0.5% chance of winning. Yet if those odds are well-priced (good value), the strategy may still be profitable — albeit very high risk.
Whether you have a low or a high strike rate, the odds are everything. Strike rates only reveal the observed win rate — not the profitability of a betting strategy.
Value Is Key
Refining your bet selection method is the most important aspect of your strategy. That should be your focus.
You have to gauge the real probability of an event happening in order to identify “plus ev” value bets in the market, and to avoid both accurate and “minus ev” odds (which will not turn you a profit in the long run).
You can use an existing data sources to identify value odds and, in turn, improve the strike rate to beyond what is expected. I recommend checking out: