Magician-turned-mathematician uncovers bias in coin flipping (2004)
For those interested in games of chance, I&#x27;ve been playing around with Betfair&#x27;s Exchange Hi Lo card game [1]. I came up with an algorithm to, given a game state, quickly compute the odds of all subsequent outcomes in polynomial time.<p>Based on this algorithm, I&#x27;ve been building a bot [2] to integrate with Betfair&#x27;s games API to play automatically for me.<p>After finishing the first iteration, running it for a bit and losing a few Euros, I quickly realised that some of my assumptions as laid out in the README were wrong (I will be updating this soon). Namely, I wasn&#x27;t accounting for Betfair&#x27;s commission on winnings (silly me). I currently have an EU-based account, which has a 6.5 per cent commission on winnings. UK-based accounts have the minimum at 5 per cent. The commission has an effect on the cheapest profitable odds you can provide, which has an effect on whether people want to match bets at those odds.<p>With this in mind, it quickly becomes clear that any unmatched bets you see in the market are far from the maximum profitable odds. This makes sense, and competing based on odds becomes impossible at this point. I am led to believe that the only way to make money is by having a UK-based account plus getting the bets to the market first. I have a few ideas on how to do this.<p>If I can get the bets to match at odds that guarantee profit in the long-run assuming UK-based commission of 5 per cent, then I&#x27;m going to call it a day.<p>Regardless, I&#x27;m not expecting to make too much money from this. I have a lot of free time right now (looking for a job), so if anyone wants to get into anything else available on Betfair together, then please get in touch at the email on my Github through [2]. My discrete probability and programming are okay, but it would be great to have someone who could share their statistics knowledge.<p>[1] <a href="https:&#x2F;&#x2F;games.betfair.com&#x2F;exchange-hi-lo&#x2F;standard" rel="nofollow">https:&#x2F;&#x2F;games.betfair.com&#x2F;exchange-hi-lo&#x2F;standard</a><p>[2] <a href="https:&#x2F;&#x2F;github.com&#x2F;jpcooper&#x2F;betfair-exchange-hi-lo-odds" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;jpcooper&#x2F;betfair-exchange-hi-lo-odds</a>