Mitchell movement

Let us clarify what we are dealing with in a duplicate pairs' tournament movement. Pairs' movements have three basic interacting groups: the boards, the tables and the pairs. The tables are the basic or trivial group and are stationary. In a Mitchell movement, the pairs consist of two sub-groups: the N-S pairs and the E-W pairs.

Therefore a Mitchell movement has 4 groups in all: N-S pairs, E-W pairs, boards and tables. The number of tables equals the number of N-S pairs which in turn equals the number of E-W pairs. The number of boards is a multiple of the number of tables. It is also possible for N-S pairs to equal E-W pairs minus 1 or E-W pairs plus 1, commonly called the half table movement.

The objective of the Mitchell movement is for all the N-S pairs to meet all the E-W pairs while all pairs play all the boards. This will be so only for an odd number of tables. This is achieved by one group remaining stationary (together with the tables), while another group moves up one table and the final group moves down one table.

The normal procedure, as defined by Mitchell, is for the N-S pairs to remain stationary, the E-W pairs to move up one table, and the boards to move down one table. The advantage of moving the boards, instead of their remaining stationary, is less movement of people around the room at change time.

With the boards stationary and both groups of pairs moving, there is the advantages the boards will never be misplaced, and the pair numbers (both N-S and E-W) are in sequence and errors are obvious in entering pair numbers on traveling score-sheets.

Too much movement during the change tends to spoil the event. On the other hand, if a movement is using more than one room, then keeping the boards stationary is highly recommended (also see switched Mitchells, page 154).

As it is quite clear that no pair meets another pair sitting in the same direction, there will be two winners. Mathematically, this does produce the ideal situation: each pair being compared with the same set of pairs on each board and all pairs playing all boards. This movement is then said to have perfect comparisons.

The following schedule will help clarify these points. This is the very simple case of a three table Mitchell. The N-S and E-W pairs are shown, for example, as 2-3 respectively. The board-set no. is shown as (1). Here 1 indicates a set of boards numbered 1 through 8 or 1 through 9 etc., depending on the number of boards in the movement (24 and 27 in these two cases).