Variation and problem solving

The key to Deming's ideas on quality lies in his recognition of the importance of variation. In Out of the crisis he states:

'The central problem in management and in leadership...is failure to understand the information in variation'.

Deming was preoccupied with why things do not behave as predicted. All systems (be they the equipment, the process or the people) have variation, but he argued that it is essential for managers to be able to distinguish between special and common causes of variation.

He developed a theory of variation - that special causes of variation are usually easily attributable to quickly recognizable factors such as changes of procedure, change of shift or operator etc, but that common causes will remain when special causes have been eliminated (normally due to design, process or system).

These common causes are often recognized by workers, but only managers have the authority to change them to avoid repeated occurrence of the problem.

Deming estimated that management was responsible for more than 85% of the causes of variation. This formed his central message to the Japanese.