Tool: Control Chart 2
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Identifying Special Causes of Variation
source: Brian Joiner, Fourth Generation Management, pp. 260.
See also Lean Six Sigma
Pocket Toolbook, p. 133-135.
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Strategies for Reducing Special Causes of Variation
• Get timely data so special causes are signaled
• Put in place an immediate remedy to contain any
• Search for the cause -- see what was different.
• Develop a longer term remedy.
source: Brian Joiner, Fourth Generation Management, pp. 138-139.
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“In a common cause
situation, there is no such
thing as THE cause.”
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Improving a Stable Process
• Stratify -- sort into groups or categories; look for
patterns. (e.g., type of job, day of week, time, weather,
region, employee, product, etc.)
• Experiment -- make planned changes and learn from
the effects. (e.g., need to be able to assess and learn
from the results -- use PDCA .)
• Disaggregate -- divide the process into component
pieces and manage the pieces. (e.g., making the
elements of a process visible through measurements
source: Brian Joiner, Fourth Generation Management, pp. 140-146.
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