Zoo Clan - Clan Ladder

OVERVIEW
Zoo Clan maintains both a win/loss record and a rating for each player who plays in ladder games (duel matches). Players gain rating points for each win, and lose rating points for each loss. Because ratings take into account not only the number of wins and losses but also the skill of each opponent, they are a useful measure of the true skill level of a player.

The rating system used by Zoo Clan is the same Elo rating system that is used in competitive chess, golf, tennis, and Battle.net. The Elo rating is a scientific model which provides a meaningful way to compare the skill level of different players, based on the assumption that skill levels follow a normal bell curve.

LADDER GAMES
Only ladder games count towards your rating and ladder standing.

PROBABILITY OF WINNING
Zoo Clan will compute the probability of each player winning a ladder game based on that player's rating and the ratings of each of the players he is playing against. This probability is used to determine how many rating points the player wins or loses for winning or losing the game. A player who wins against a much higher rated player will gain many points for the victory, while a player who wins against a much lower rated player will gain very few points.

For two player games, the following formula is used to compute the probability of winning:

Probability = 1 / (1 + 10^(-difference_in_ratings / 400))

You can use the following charts to quickly estimate your probability of winning against another opponent:

When playing a HIGHER rated player:		When playing a LOWER rated player:
Rating Difference	Probability of Winning	Rating Difference	Probability of Winning
400	9.1%	0	50%
350	11.8%	50	57.1%
300	15.1%	100	64%
250	19.2%	150	70.3%
200	24%	200	76%
150	29.7%	250	80.8%
100	36%	300	84.9%
50	42%	350	88.2%
0	50%	400	90.9%

DEVELOPMENT COEFFICIENT
Each player is assigned a development coefficient (K), which determines the maximum number of rating points that can be won or lost in any one game. The development coefficient starts at 50 and then drops lower as the player becomes more experienced. This enables new players to move quickly towards a rating that reflects their true ability level, while adding a level of stability to the ratings of more experienced players.

The development coefficient is calculated according to the following rules:

K=50 for new players
K=30 for players who have played 30 or more ladder games
K=20 for players who have attained a rating of 2400 or higher

RATING CHANGE
Each player who completes a ladder game wins or loses points according to the following formulas:

Winner's rating increases by K * (100% - probability_of_winning)
Loser's rating decreases by K * probability_of_winning

Any player ranked in the top 10 can only gain rating points by defeating players ranked in the top 5.

LADDER
The top 5 rated players in the clan are given official rankings on the ladder. Ladder rankings are recomputed every night at midnight Pacific time.

The results of ladder games are automatically posted to:

Zoo Clan Ladder

All ladder matches are posted to the appropriate forum.

LADDER ABUSES
It is considered an abuse of the ladder system to:

Play more than 3 illegitimate games against any person within 6 hours. Examples would be playing a 5-minute game then surrender, one player not attacking, repeatedly surrendering when there is no need, etc.
Winning / Losing more than 3 legitimate games to the same person within 6 hours. This allows you to have a "best two out of three" match against someone. Any more than this, and it will be considered abuse.

Zoo Clan may, at its sole discretion, reset the record of an account of any player suspected of abusing. We may also reset an account's record due to the following actions:

Attempting to abuse the Ladder system.
Playing Ladder games in such a way as to undermine the spirit of competitive play.

The results of all ladder games are posted to:

Zoo Clan Ladder

Any interested observer can easily check the record of a ranked player to see if he/she is repeatedly playing against the same opponents or consistently disconnecting from games.

SCREENSHOTS
Each player must save a screenshot of the chat commandand send it to gukar_x@hotmail.com for offical recording of ratings. If no player sends a replay in, the players will not recieve credit.