Scalping the serve and EV calculations

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Bluesky
Posts: 420
Joined: Mon Sep 19, 2016 9:26 pm

I was recently watching PWs Scalping the serve on a tennis match video on Youtube here is the link for anyone who has not seen it and would like to check it out.

https://www.betangel.tv/videos/trading- ... nis?jut1=2

I thought it might be interesting to do some expected value calculations (EV calculations) using the odds occurring in the video to see what happens. It’s very easy to make mistakes when doing these calculations so if anyone spots some please let me know. The calculations are showing that over the long term this trade would not be profitable, I therefore assume I have made one or more mistakes somewhere. I can’t however see where I have gone wrong so I would really appreciate it if someone could have a quick look at what I have done and let me know what is wrong.

Here is the information taken from the video that I will be using in my calculations:-

We are going to back Sam Querrey at 3 with £100 to win his next service game (in the video Peter used £500 but I’m going to use £100 to make the maths a little easier). Sam has just lost the first set and we are about to start the first game of the next set with Sam to serve.

Tennis trader is telling us that if he wins his odds are likely to come in to 2.85 this is the value I am going to use in the following calculations (in the video Querrey did win and Peter traded out at 2.86).

Our greened up profit if the odds come in to 2.85 will be

100[(3-2.85)/2.85] = £5.26

Tennis trader is also telling us that if he loses this game then his odds are likely to drift to 4.34 so we need to work out what loss we will have to take if this happens.


100[(3-4.34)/4.34] = £30.87 Loss.

Tennis trader also gives us the probabilities of him winning and losing this game, the probability that he will win is 83.3% and that he will lose is obviously 16.7%.

We can now use these probabilities to work out the EV of this trade.

£5.26 X 0.833 - £30.87 X 0.167 = Loss of £0.77

So over the long term if we do this trade we will lose 77 pence for every £100 we back with, this does not take into account the commission we will have to pay Betfair.
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Dallas
Posts: 22674
Joined: Sun Aug 09, 2015 10:57 pm
Location: Working From Home

Bluesky
Posts: 420
Joined: Mon Sep 19, 2016 9:26 pm

Thanks for the link Dallas, I wasn't all that pleased that I my calculations were correct I was really hoping I had made a mistake and the long term value of that trade would have been profitable. I guess tennis trading isn't as easy as I was hoping it might be.

I have been looking at the example trade you posted here

http://www.betangel.com/forum/viewtopic.php?f=7&t=13251

Take a look at these simple calculations they seem to be telling me that this trade too would not be profitable over the long term, using the figures you displayed from tennis trader in the post.

If Elias breaks Thiems serve then you make £75 and if he doesn't then you lose about £16, risking £16 in order to win £75 sounds good but don't we need to take into account how often each outcome is likely to take place. From Tennis Trader I think Thiem is going to hold his serve in this game 90.6% of the time and Elias break only 9.4% of the time.

If we use these stats we can work out the EV of this trade.

£75 X 0.094 - £16 X 0.906 = Loss of £7.44 over the long term on this trade. Am I missing something really important here, have I made an maths error or are you taking something else into account which you have not mentioned in your post?
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