Re: Cause source - system v. employee

[wayne.mack@pec.com]

My understanding of control charts is that the only time that a cause for a variation can be objectively identified is when a special cause has occurred.  The criteria used is timing, what happened just prior to the change in the data?

I see root cause analysis as something that can be applied to either common or special cause variation.  In the case of common cause variation, however, the result of the analysis is a hypothesis and further experimentation is required to make an objective determination.  This is done by correcting the suspected cause and verifying that a special cause variation occurs on the control chart immediately following the change.

Does this help clarify what I am tryi to express?

Wayne Mack
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