Calculation of new ELO takes partner game into account

[tiegerstochter]

I wanted to raise the topic o new ELO calculations in Tichu. Right now, your rank is compared to all other players, including your partner. If that player has a higher rank than you, your rank increases, but if they have a lower ELO your rank decreases. However, it is not possible to win against your partner.
One solution would be for players who care much about their rank not to play with beginners, but I don't think that is a community friendly solution. Instead, is it somehow possible to just not include the ranking against your partner in the ELO calculations?

[NeanderthalMan]

Is this true? I've never had ELO decrease with a win and I'm often higher than my partner. With significantly lower opponents, the increase may be +1 to +6 but never negative.

[ufm]

Is this true? I've never had ELO decrease with a win and I'm often higher than my partner. With significantly lower opponents, the increase may be +1 to +6 but never negative.

https://boardgamearena.com/bug?id=11297

Sadly it is.

[tiegerstochter]

Right, the overall ELO does not decrease, so it is not obvious to see. If you hover about your ELO evaluation on the end game screen, you will see a detailed explanation for the new ELO rank. I only started to do this, because I was curious about that ominous number.

Thank you for the link to the bug. I guess, we will have to leave it to the that and see what happens

[NeanderthalMan]

Right, the overall ELO does not decrease, so it is not obvious to see. If you hover about your ELO evaluation on the end game screen, you will see a detailed explanation for the new ELO rank. I only started to do this, because I was curious about that ominous number.

So you're saying the net ELO increase you receive is reduced by some marginal amount if you outrank your p because it's considered a tie, whereas the otherside of the partnership gets a marginal increase from the tie.

What is the solution to the ELO formula and would it be retroactive? I imagine it'd throw off all the current and historic leader boards if it was.

[tiegerstochter]

If the team wins, then you are right. The "marginal" depends on the ELO difference to your partner. But I think, it is more obvious, when you consider the situation, when you loose due to a weaker player. Then you would get more points subtracted from your ELO than your partner, as they "at least" tied against a higher ranked player (independently of the ELO gain or loss calculated from the opponents).

I normally don't care too much about my ELO, and hope, that this is true for the majority of players, but it can be annoying.

The bug, ufm linked, tells us, that this issue came up 2 years ago. The solution should be simple. When a player is marked as partner, don't use their ELO to calculate your new ELO rank. I don't think that it would or should be retroactive. That would be quite unfair and unnecessary.

[zyrain]

This is still an issue. I just posted a bug on it. copied below:

Here's how the game calculated my ELO:

ELO Rank before this game 217.11

Victory against Inrrrr (100) Probability of a win: 66% +9.11
Victory against kiss... (240) Probability of a win: 47% +14.41
Tie with grill... (64): Probability of a win: 71% -5.58

Total ELO variation 17.72

ELO Rank after this game: (234.83)

It's a problem to report a tie, leading to ELO loss in this situation. This is because it encourages good players to not play with beginners, which isn't community friendly. It's harder to win with lower rank teammates and this does the opposite.

One solution is to use the average rank of both members of the team for the calculation against the other team to provide the win probability, then apply that probability equally.

For example:

Your team (217) & (64) = average (141)
Victory against Inrrrr (100) & kill (240) = average (170)
Probability of a win: 46% +10.8

[NeanderthalMan]

Individual ELO formula should just exclude partner ELO entirely and only be calculated relative to opponents.