Committees differ enormously in their size, composition, frequency of meetings, how they were set up, in their purpose and objectives, and in their rules of procedure. Also implicit in the concept of a committee is the doctrine of collective responsibility. Members of a corresponding British committee may feel distinct reservations towards each other socially and yet believe that each member is entitled to voice his personal views before the group view is formed. An advantage of the British outlook is that a decision once reached is less likely to be queried later by any member of the committee or to be reversed on a change of Chairman. Committees can be classified according to their time scale, purpose, and composition. Standing Committees meet usually at regular intervals, monthly or quarterly. Ad hoc Committees usually have a fairly rapid succession of meetings until their particular task has been accomplished.