Need help calculating in-play odds.

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Posts: 2
Joined: Fri Oct 11, 2019 6:51 pm

Hello guys,
I have math related question I guess and I hope some of you might help me out with this :)
All of this is just a theoretical example I can't get my head around. I will try to explain it as clearly as I possibly can since my english i pretty poor :)

Lets say that data from 1000 matches suggests that at the beginning of match each player has 50% chance of winnning, since one player has to win and other has to loose. Therefore we get 1000 winners and 1000 loosers.
Now let's assume that data gathered from these matches 80% are won by the player who won first set.
So if a player wins first set his chance of winning tennis match goes up to 80%, if he loses first set it goes down to 20%.

This all seems simple to me if both players has same chance of winning at the beginning of the match. This corresponds to fair odds of 2 for each player. After first set the winner should have fair odds of 1.25 (80 % chance), and the looser should have fair odds of 5 (20% chance).

But how to calculate odds after first set if at the beginning of the match players have odds of 1.43 (70% chance) and 3.33 (30% chance) for example?
How should the odds for these players change after first set if they win/loose?
Hopefully this is well enough explained for someone to understand what I meant.
Thanks in advance guys!
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Posts: 9290
Joined: Wed Aug 30, 2017 11:44 am
Location: UK

Hi gacho, welcome to the forum.

It's possible to come up with a generalised algorithm from data or simulations but it's quite complex. Have you thought about using the Bet Angel Tennis Trader, which should give you this information for any particular tennis match?
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Posts: 15291
Joined: Sun Aug 09, 2015 10:57 pm

Derek is right in that TT will do all this work for you, but as a general rule of thumb is if the fav goes a break up there odds will half, then if they win the first set there odds will half again

So if they start at 1.60
after 1st break 1.30
win first set 1.15
Posts: 2
Joined: Fri Oct 11, 2019 6:51 pm

Thank you guys for answering.
I am aware of tennis trader, but was just wondering how to calculate the ods myself. Not as simple as i thought :)
Posts: 91
Joined: Thu Aug 22, 2019 5:25 am

Hi Gacho

I have built an in play odds predictor table which need refining and checking - this one was done for the underdog

I am hoping others can also give input

Let me know on your thoughts
Predict table .xlsx
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