Committees are highly individual, and any generalizations about them should be made with great care. Some aspects at least of the different methods used by different committees should be subject to controlled experiment, with a view to determining which methods help to make the committees most efficient. Examples of committees which use the first method are local authority Councils, and Resident Association committees; and of those which use the second method informal ad hoc business committees, Inter-Services study groups and Quakers. Joint committees require special mention, since it might be thought that they must necessarily operate within special constraints. The Chairman has authority to ensure that preference is given to those members who can make the most useful contributions, so that committee time is occupied as efficiently as possible. The Chairman controls the proceedings so as to achieve precise objectives.