Arbusers

Hi members

Hopefully you can help me out here.

I am wondering why there often is so diverse estimates among the books when it comes to the line games odd/even? Like with the game Mensik - Fritz tomorrow. The odds at even range from 1.75 to 2.5 and odd from 1.50 to 1.87. And they are steady.

I did a simple model using the data from this match. A simulation 1 million times using 2 assumptions:
The outcome is based on the normalized probalilities from the average market odds of the 1st set, correct score line.
Any subsequent sets have similar distribution of odds on the outcomes as the first set.

It is a grand slam, so no game stops before any player has 3 set points of course.

When I run this simulation I get probabilities 50.3% for odd and 49.7% for even. Had it been a regular ATP where winner needs 2 set points I would get 48.4% for odd and 51.6% for even.
When I run the simulations again I get the same results, so 1 million repetitions is enough.

For the match in question Bet365 is offering 1.5 for odd and 2.5. This is SO far from the nearly 50/50 outcome that the simple simulation shows.

So what am I missing here. I think some books must have a reason for not offering just 50/50 or odds 1.9/1.9. There must be something very significant that plays a role here.

Any suggestions?

I have not had a look, but could it be because of different ruling?

And my first thought is that odd should be favorable because of the chance of tiebreak, but its a quick guess

Lumberjack wrote: ↑

Thu Aug 31, 2023 5:34 pm

I have not had a look, but could it be because of different ruling?

And my first thought is that odd should be favorable because of the chance of tiebreak, but its a quick guess

Maybe there's something about ruling, but what could it be? It is quite obvious that a tiebreak must count as 13 points as the result on the score board is either 6-7 or 7-6 and in the simulation those two outcomes, and their probabilities, are included. In total there are 15 different outcomes of a played set and they are all included.

How come there are 15 possible results? I only counted 14: 6-0; 6-1; 6-2; 6-3; 6-4; 7-5; 7-6; 0-6; 1-6; 2-6; 3-6; 4-6; 5-7; 6-7. Out of these 14 there are 8 even and 6 odd results.
So for a single set the even should be a favorite.
But for a match it gets more tricky especially in a best out of five

Sandica9 wrote: ↑

Thu Aug 31, 2023 8:27 pm

How come there are 15 possible results? I only counted 14: 6-0; 6-1; 6-2; 6-3; 6-4; 7-5; 7-6; 0-6; 1-6; 2-6; 3-6; 4-6; 5-7; 6-7. Out of these 14 there are 8 even and 6 odd results.
So for a single set the even should be a favorite.
But for a match it gets more tricky especially in a best out of five

Thank you for pointing that out. You're right. I made a mistake by counting the header on my list.

The even, although it represents 8 outcomes, is not a favorite for the 1st set alone, at least for this match. The probability, Mensik x Fritz, for a even 1st set is 42.5%. But it turns out that when taking one set a a time with these probabilities in a monte carlo simulation until one player has 3 set points, the chances of odd and even for the entire match are practically the same. At least for me. If anyone would like to quality test this, here are the market odds and probabilities I used.
As mentioned initially, one assumption is that the correct score odds are true and will represent the probabilities. But I find it hard to believe that they should be so wrong that they could be the cause.

Hello, I am going to try to explain but I don’t know if I will be able in English.

First of all, Fritz always choose to serve in the coin toss and the opponent always choose to receive in the coin toss, so the odds in correct score 1st set are based in that is almost sure that Fritz will start serving in first set and he is a big favorite. That is the reason for 6-3 Fritz is the shortest odd in that market (start serving + 1 break).

The problem that the odds for the correct score second set are not the same because is most probably that Fritz will start receiving and the shortest odd for correct score for second set will be 6-4 for Fritz. Approximately, the odds for even-odd in second set will be the opposite to the 1st set.

For the 3rd set, the odds for even-odd again will be the same that for the 2nd set because it will be most probably that Fritz will start receiving.

So, the main problem is that the odds for the correct score in 1st set are not the same that for second set because are based in who start serving and one player is the big favorite.

jacampillocc wrote: ↑

Fri Sep 01, 2023 3:37 pm

Hello, I am going to try to explain but I don’t know if I will be able in English.

First of all, Fritz always choose to serve in the coin toss and the opponent always choose to receive in the coin toss, so the odds in correct score 1st set are based in that is almost sure that Fritz will start serving in first set and he is a big favorite. That is the reason for 6-3 Fritz is the shortest odd in that market (start serving + 1 break).

The problem that the odds for the correct score second set are not the same because is most probably that Fritz will start receiving and the shortest odd for correct score for second set will be 6-4 for Fritz. Approximately, the odds for even-odd in second set will be the opposite to the 1st set.

For the 3rd set, the odds for even-odd again will be the same that for the 2nd set because it will be most probably that Fritz will start receiving.

So, the main problem is that the odds for the correct score in 1st set are not the same that for second set because are based in who start serving and one player is the big favorite.

Thank you. That makes much sense and might be the main reason bet365 chose to offer 2.5 at the even outcome. They have adjusted their odds to 2.25 now though, so maybe it was too generous after all. Some of the books that offered 1.9/1.9 initially are now 1.8/2.0.

In summary, I think the situation you describe is the main cause. Then some books overreact while others do not take it into account at all. Now it seems like books are approaching each other as the match is coming to a start.