Editing Duplicate bridge (section)

===Table movements===
{{See also|Duplicate bridge movements}}

The '''[[John T. Mitchell|Mitchell]] movement''' is the most common. The North-South pairs remain stationary. After each round, the East-West pairs move to the next higher-numbered table and the boards move to the next lower table. If the number of tables is odd, every E-W pair will play different boards against every N-S pair after the full circle. In case of an even number of tables, the East-West pairs are told to skip a table after about half the rounds so that they do not encounter boards that they have already played; alternatively ("Relay-bystand Mitchell"), a "bystand" (playerless table) is introduced, while the two tables farthest from the bystand share the boards in each round (the "relay"). Usually, the bystand is placed halfway through the field (e.g. between Tables 5 and 6 if there are 10 tables) and the relay between Table 1 and the last table. A "perfect" Mitchell is seven, nine, or thirteen tables, with four, three, or two boards per round respectively: all players play all boards, and all pairs of each direction play against all pairs of the other direction. A variation of the Mitchell movement employs "arrow-switching". This means that for approximately one-eighth of the boards played, the N-S pairs play the E-W cards and vice versa. This variation is used when it is desired to have one winner rather than two winners (see below).

The '''[[Edwin C Howell (whist and bridge player)|Howell]] movement''' is sometimes used instead, usually when there are a relatively small number of tables. This movement is more complicated and varies according to the total number of pairs. All boards and most pairs move after every round according to guide cards placed on the tables, or carried by the players (usually one pair, or sometimes more, remain stationary). The Howell is sometimes considered a fairer test than the Mitchell, because each pair faces all or nearly all of the other pairs, not just the pairs sitting in the opposite direction. However the fairness of a movement depends not only on who one plays against but also to a considerable extent on one's indirect opponents, i.e. those who play the same cards as you do. The Howell also tends to be more error-prone than the Mitchell due to its greater complexity. Ideally the number of rounds will be one less than the number of pairs competing, so that each pair plays one round against every other pair. Each round will usually consist of either 2, 3, or 4 boards. However, sometimes this produces an inconvenient total number of boards to be played. To avoid this, a "reduced Howell" or "three-quarter Howell" movement is often played, with fewer rounds and usually with more than one stationary pair, so that the number of rounds plus the number of stationary pairs equals the total number of pairs.

Less common is the '''Chalfant movement'''. In this movement, the boards remain stationary while the players move according to guide cards. This requires significantly more physical tables, because several tables are not in play on any given round. (Like the Howell movement, this movement is typically used when there is a relatively small number of players, typically no more than 12 pairs. Also like the Howell movement, this movement produces a single winner and pairs face all or almost all of the other pairs in play.) This movement has the advantage that pairs are often moving to a table that was not in use on a previous round, so a slow pair does not delay as many other pairs as in a Howell. Also, for several sizes, this movement is technically superior in that more pairs face all other pairs than in the corresponding Howell movement. This movement has the disadvantage of requiring a larger number of physical tables, and thus more space. It also requires the players to carry guide cards with them and consult them, while the guide cards usually remain on the tables for Howell movements.

Whatever movement is used, if the number of pairs is odd, obviously one pair must sit idle during each round; that situation is referred to as a ''[[bye (sports)|bye]]'' or ''sit out''. In that undesirable case, the missing pair (sometimes called the ''phantom pair'') is treated as if it exists, i.e. the movement is set up for (number of actual pairs + half a table). The phantom pair may be North-South, East-West or an arbitrary pair number in a Howell movement. In a Mitchell movement, having an East-West phantom pair is advantageous in that there are non-phantom players at each table responsible for correct movement of the boards. During the movement, one pair in each round will sit out ("play" against the phantom pair). Since, as result, pairs will usually play unequal numbers of boards, their final results are normally scaled in the final calculation (known as ''factoring''), or less commonly they might be awarded "bye points" for that round (normally, a result slightly above average).

Another arrangement for an odd number of pairs is called a ''bump'' or ''rover'' movement, in which the number of tables is rounded down to (number of actual pairs - 1)/2.  In a Mitchell movement, the extra pair normally sits out the first round and then, according to a schedule, substitutes for a different North-South pair for each subsequent round (the "bumped" pair having a sit out for that round). The extra pair are frequently referred to as the "rover pair" because, unlike the other North-South pairs, they move at each round. In particular, the bump is preferable to the sit out for 11½ tables: it allows every pair to play at least 24 boards while having only 33 boards in play.

In a Howell movement, the extra pair normally sit out the first round and are then allocated fixed seats where they remain for all subsequent rounds. Any position other than that which would normally be occupied by a stationary pair will do. The extra pair thus displace, or "bump", a different pair (those who would normally move to those seats) at each round. The extra pair are still colloquially known as the "rover pair" even though, in a Howell, they do not actually rove.

A better alternative is for the phantom pair to be allocated a stationary position. This enables all the boards to be played the same number of times (so that all the pairs play all the boards) and the movement in many cases to be completely fair between all the non-stationary pairs.

'''Trials''' are usually reserved for high-level competitions (such as regional and national championships, invitation tournaments etc.). There, a fixed number of pairs (usually 16) play a full [[round-robin tournament]] ([[Swiss tournament|Swiss]] can be also used to shorten the tournament) with relatively long matches (8-32 boards) against each other, the entire tournament lasting for two to four days. One session consists of only one round, with boards circulating among the tables and pairs remaining seated. Results are calculated after each round using IMP or Calcutta scoring, converted to Victory points, and added up to the running score. The pair with highest VP score becomes the winner.