Common Cause

Definition of Common Cause:

A source of quality failure that is always present as part of the random variation inherent in the process itself.

Its origin can usually be traced to an element of the process which only management can correct.

The less well-defined a process is, the more it is subject to random variation, resulting in a higher level of quality failures (bugs).

In general, and very approximately, common causes outweigh special causes as origins of quality failures by four to 1 (Pareto distribution).

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