Section 2 Variation Fundamentals
Lesson S02-03
Text: Section 2 pages 10 – 15
Duration: 20 minutes
All of the discussion regarding variation has been leading up to a fundamental concept for controlling variation. It is the notion of control limits.
Control limits represent the range over which the data is expected to fall. That is, control limits are limits of expected variation. More specifically, it is expected that 99.73% of the statistics we monitor will be within the control limits.
A special cause source of variation is any source that results in unpredictable behavior, i.e. anything unexpected. Often, the term “assignable cause” is used instead of “special cause.”
Specification limits often appear on a blueprint in industrial applications. In manufacturing, specification limits are generally dictated by a customer or product design engineer.
Conceptually: The Idea of a Control Chart
The Difference Between Specification Limits and Control Limits
By Whom or How are specification limits determined?
A. They are fixed by policy, often at ±10%
B. The designing engineer establishes the specifications
C. The specifications are set by copying values from the datasheet
D. Not sure
Review of Specifications vs. Control Limits
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