(Bridge bidding box)
Bidding and convention systems
Combinatorial richness of the bridge allows to implement, in accordance with the rules, various techniques to communicate information, both in the bidding phase than that of the card play. These techniques are conventions established by prior agreement between partners who attribute a special meaning to certain types of results or certain configuration of cards.
The bidding conventions, among which the best known are the Stayman, Blackwood and Texas, lead to the development of a system, a true language. Among the best knownare are the fifth major suit, Acol, Standard American Yellow Card (SAYC), and mainly artificial systems such as the Precision Club and Strong Diamond, etc.
These systems are all based on valuation techniques. How to play the cards can also be subject to conventions.
- the transmission of information between partners in bridge is in no way a cheating, but a technical way to implement the rules in their absolute respect;
- and the information transmitted this way is public, that is to say, any agreement between partners must be effectively communicated to opponents and, at their request, clarified and specified.
Like most card games, bridge is a game of chance. However, to reduce the share of luck and allow competition, for the talent of the players to express themselves, everyone’s score is compared to that of others. There are two main systems (duplicate bridge):
- the tournament in pairs
- the match by four
Tournament in pairs
In a tournament in pairs, players are not fixed.
- Mitchell movement type: players of a given line – generally east-west – circulate from table to table; at the same time, the deals rotate in opposite directions. Ultimately, each deal is played the same number of times; depending on the number of tables, each pair will play or not all deals, and will compete all or part of pairs of the other line.
- Howell movement type: in this type of movement, sometimes a pair will be North-South, East-West sometimes. Each pair follows a movement plan known in advance which led him to meet with other pairs. The deals are fixed, that is to say, they remain on the tables where they are played, there are the pairs that move. This type of movement is generally used when the total number of pairs does not allow to organize a Mitchell-type movement.
It then compares the results line by line: on one side, all the North-South, on the other, all the East-West when Mitchell movement, or a single list in case of Howell. They are classified by deals, and by score within each hand. On each deal, each pair scores two points (MP for Match Point) for each additional pair that had a lower score and one point for every other pair who made the same score. These points are added to determine the winners. You can count differently, assigning to each give a score equal to 2x (<number of tables> – <place>), which is the same. This formula focuses instead on the score.
The final scores are given in percent, a result between 0 and 100%: 100% is the best result, it means that the pair played all data strictly better than all other pairs; 50% means that the pair has played an average of all data like any other, and 0% meaning that the player is the only pair to have had the worst result. In practice, the vast majority of pairs terminate with a score between 40 and 60%.
Percentage calculation on a deal
It is decided a maximum score; it will be the number of pairs of players participating in the tournament, decreased by 1. This score is then awarded to the best player, then one point less for the next player and so on to the last. In case of a tie, we sum their points and divide by the number of tie, each marks the resulting figure. Everything is converted to percentage: multiply the points by 100 and divided by the maximum number of points.
Taking as an example the results of a tournament including 9 pairs of participants: the worst score is 110, 1 pair scored 140, 2 got 170, 4 got 620, the best pair reached 650 points.
The points obtained will be:
- 0 points for the pair of players who have reached 110, which will give: 100/8 X 0 = 0%
- 1 point for those who have reached 140, which will give: 1 X 100/8 = 12.5%
- (3 + 2)/2 is 2.5 points for teams scoring 170, giving 2.5×100/8 = 31.25%
- (7 + 6 + 5 + 4)/4 = 5.5 points for those scoring 620, giving 5.5 x 100/8 = 68.75%
- 8 points for the maximum score 650, giving: 8 x 100/8 = 100%
Match with four
In a game with four, two teams of four compete on the same deals, crossing lines (North-South team A plays against East-West team B and vice versa). Then compared, deal by deal, the score of the two teams: converting the difference in scores between the two teams in ‘international match points‘ or IMP as a standard conversion table. These match points are added together to determine the winning team. If the competition is part of a championship, the final difference in IMP is converted into victory points according to a specific key for each championship (but in highly standard practice by number of deals played during the game).
In this formula, it is the differences that count, and strategy differs slightly but significantly from that of conventional pairs tournament.
Matches with four are used to support various forms of competitions, including:
- matches by knockout,
- tournaments hens, in which each team plays each other,
- the Pattons, in which each team plays a subset of the other, in an organized way to approach as much as possible equity.
This is, in short, a pairs competition where the points are counted (almost) in game by four. There are two main variants:
- each pair is compared in IMP to each other pair and then divides the result by the number of pairs (or whatever number minus 1), or
- each pair is compared in IMP to a median score (or, more rarely, to a score)
It is also common to ignore the most extreme scores (eg 5% highscore and 5% worse scores).
Rules of competition
Above the “base” rules of the bridge, are grafted rules (or “laws”) of competition. Each federation shall promulgate its own rules which apply in the competitions it organizes. The other competition organizers usually implicitly or explicitly use the rules issued by the national (or regional) federation corresponding to the location of the competition. Some organizers added some rules or listing requirements (for example to create a tournament for “beginners”) while others do not refer to any comprehensive settlement and prefer then the saying “in case of problems, check with the organizer who will advise as he pleases.”
In practice, except at high level, it is not really necessary to know the rules to play in competition and even high-level, it is not necessary to know them completely.
The rules mainly cover three requirements:
- Maintain compliance with certain ethical rules. (It is as such forbidden by most federations to pretend to hesitate when you have only one card in the suit)
- Find means to ‘save’ the situation when a player inadvertently breaks a rule. (For example, when a player has played a card while it was not his turn to play)
- Protect beginner or intermediate players by the complexities of some auction systems used by some players. (So most federations prohibit certain very inaccurate and/or artificial auction agreements in some levels of competition.)
Translated from Wikipedia