RE: Methods to Determine Special vs. Common Cause (fwd)

[Larry Quick <lquick@admin.aurora.edu>]

Vic,

To me a special cause of variation is one that emanates from outside of a
system and impacts only one or a limited number of system outputs (Ex.
loaves of bread produced by a bakery). Only one or a limited number of
loaves is affected by the special cause impacting the system emanating 
from outside the system.

To me a common cause of variation is a source of variation that is built
into the system itself and impacts each and every system output to a
grater or lesser extent. (Ex. room humidity in a bakery). Every loaf
produced is impacted to a greater or lesser extent by the room humidity of
the bakery.

Larry  

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*   Laurence J. Quick, Ph.D., CPA                       *
*   Director, Quality and System Management Program     *
*   Aurora University                                   *
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