|
Team Games
Q: I am always playing together in the same team with my friend JoeDoe. Will the TrueSkill ranking system be able to differentiate between us two in terms of skills? In other words, is the TrueSkill ranking system capable of finding that I am the more skilled player of us two?
A: If both you and your friend only play ranked team games together then the TrueSkill ranking system cannot distinguish between you two; it always compares the team's skills (sums of the player's skills in the teams) and 'distributes' the gain/loss proportional to the individual player's uncertainties (see detailed description). But note: if your friend also plays team games with anyone other than you then the TrueSkill ranking system will be able to identify the more skilled player of your two. Also, if both of you always only play together, you might consider forming a clan.
Q: Why does it take so many more games until convergence if I play a team game as opposed to a Free-for-All game?
A: The problem is that very little information about the individual player's skill is contained when only exploiting which of two teams wins or if the two teams draw. This is effectively only up to 1.6 bit of 'information' that needs to be 'shared' between all players participating in the game. More specifically, consider these two scenarios:
- Alice, Bob, Chris and Darren play a 4-player-Free-for-All game and Alice wins against Bob wins against Chris wins against Darren. This game outcome provides a lot of information: it's fair to say that probably Alice is better than Bob, Alice is better than Chris, Alice is better than Darren, Bob is better than Chris, etc.
- Alice and Bob play against Chris and Darren in a 2-Teams-2-Player-per-Team game and Alice and Bob win against Chris and Darren. Can we still say that this mean that Alice is better than Chris and Alice is better than Darren? No! All we can confidently assert is that Alice and Bob are better than Chris and Darren. So, the team game outcome provides only knowledge about an individual's skill in conjunction with all the other team members.
Q: How will be ranked in the TrueSkill ranking system?
A: In the TrueSkill ranking system, the team skill is the sum of the skills of all players in the team. The TrueSkill ranking system has the potential to assign a negative skill to a player; if such players are added to a team, then the skill of the team goes down (because a team killer both reduces the chance to score against the other team or might even inflict negative points by suicide). Fortunately, the TrueSkill ranking system's matchmaking procedure will eventually ensure that team killer will only play each other. And this can only be a good thing.
Q: I am playing a team game and all the players in my team drop out of the game. Of course, I lose the game. Will I lose as many skill points as all the people who left me standing in the rain?
A: Unfortunately, yes. All alternative options are possible exploits for cheating:
- If the TrueSkill ranking system does not count the game at all then the losing team can always ensure not to lose points by dropping out early (entirely).
- If the TrueSkill ranking system only uses the team configurations at the end of the game then both the players that dropped would not be penalised and the remaining player can be arbitrarily boosted (that is, shortly before the end of the game all but one player drop from a team; for the update equation it would now seem that a single player has won against a team of, say, 4 players and would apply a massive positive update).
- If the TrueSkill ranking system would introduce an arbitrary lowest rank in which every player falls that drops before the end of the game, then, again, the remaining player(s) in a team can be arbitrarily boosted (he won against the losing team and all the players that dropped. This approach would penalise the players that drop, though.
But: Players who drop regularly from a team would eventually be identified by the TrueSkill ranking system as having a negative impact on the team skill and will eventually be matched with other players of that have a negative team impact. So, you should not see this happening to often if you are a player of average skill.
Q: You are saying that the TrueSkill ranking system assumes that the skill of a team is the sum of the skills of its players. I think this model is not appropriate: I am usually playing much better with people from my friends list rather than with random players. Will this assumption lead to incorrect rankings?
A: The assumption that the team skill is the sum of the skills of its players is exactly that: an assumption. The TrueSkill ranking system will use the assumption to adopt the skill points of individual players such that the team outcome can be best predicted based on the additive assumptions of the skills. Provided that you and your friends also play team games with other players now and then, the TrueSkill ranking system will assign you a skill belief that is somewhere between the skill when you are playing with your friends and the skill when you are playing as an individual. So, in the worst case, every other game is not with your friends: then you are slightly ranked too high when you play with random team players and slightly ranked too low when you play with your friends. But, if you mostly play with your friends only the system will identify your skill correctly for most of your games.
Q: Why can two players in a party not be in two different teams?
A: This would open the possibility to cheat. You could, for example, arrange to play each other and your friend always forfeits the game. This would not allow to boost you to the top of the league (try it out with our advanced interactive ranking calculator; press the After->Before button and 'Recalculate') but it would increase your skill level artificially. The TrueSkill ranking system always assumes that the game outcome is a result of your skills (in the game) and not of your skills to cheat.
Q: Does the TrueSkill ranking system reward individual players in a team game?
A: The only information the TrueSkill ranking system will process is:
- Which team won?
- Who were the members of the participating teams?
The TrueSkill ranking system takes neither the underlying exact scores (flag captures, kills, time etc.) for each team into account nor which particular team member performed how well. As a consequence, the only way players can influence their skill updates is by promoting the probability that their team wins. Hence, "ball bitches", "hill whores", "flag fruits", "territory twits", and "bomb bastards" will hurt their individual TrueSkill ranks unless what they are doing helps their team. Obviously, it is difficult to update individual players' skills from team results only. To understand the difficulty and the solution consider the following analogy: Suppose you have four objects (players), each having an unknown weight (skill). Suppose further that you have a balance scale (game) to measure weight (skill) but are always only allowed to put two objects on each side of the balance. If you always combine the same pair of objects, the only information you can get is which pair of objects is heavier. But if you recombine the players into different pairs you can find out about their individual skills. As a consequence, the TrueSkill ranking system will be able to find out about individual players' skills from team outcomes given that players not only play in one and the same team all the time but in varying team combinations.
Q: I bought a 360 for my son for Xmas, and both of us have become seriously addicted to Halo 3 on XBox Live, particularly Team Slayer matches. Basing the skill change only on the team performance yields pretty counterintuitive results. For example, I often play a string of team slayer games where I am MVP (Most Valuable Player), which means I outscore everyone. But if my team loses those games, I gain no skill. Then, I can play poorly, but if my team wins I gain skill. This lack of feedback from individual performance is frustrating and makes your skill level beholden to the performance of the rest of your team, which is usually not under your control unless you explicitly team up with friends
A: Great that you are enjoying your 360 and Halo 3.
The question you are asking has indeed been raised by quite a few people and we had many discussions about it. However, we always return to our point of view that in a team game the only way to assess someone's skill towards the team objective is to consider the team objective only. Any auxiliary measurements such as number of flags carried, number of kills, kill-death spread, etc, all have the problem that they can be exploited thereby compromising the team objective and hence the spirit of the game. If flag carries matter, players will rush to the flag rather than defend their teammates or their own flag. Some may even kill the current flag carrier of their own team to get the flag. If it is number of kills, people will mindlessly enter combat to maximise that metric. If it is K-D spread they may hold back at a time when they could have saved a team mate. Whichever metric you take, there will be people trying to optimise their score under that metric and this will lead to distortions.
Another problem is, of course, that we would like to use the skill ratings for matchmaking. The current system essentially aims at a 50:50 win loss ratio for each team. It is unclear, how individual skill ratings based on individual achievements would change the calibration of such a system.
Of course, one might use a weighted combination of team and individual measurements. However, whenever individual measurements enter the equation there will be trouble, maybe less trouble if the weight is less, but that is not really good enough.
|
TrueSkill™ Frequently Asked Questions 