It is common to learn that managers have no knowledge of the fact that many processes in their organisations are stable. They might not perform very well, they might exhibit wide variation, but they are stable. It follows that such managers have no knowledge of the fact that the processes exhibit wide variation because managers tamper.

For example, managers react to what they think is a ‘low’ number (whereas in truth the number is entirely predictable given the variation in the system) and they unwittingly increase the variation in the system.

The variation in processes affects revenues and costs, only attention to the causes of variation will reduce variation and thus improve performance.

Managers need to learn how to ‘interfere’ in more constructive ways