© 2004 Cayman Business
Systems
Rev:
Pre-G3 - Rendered Thursday,
February 12, 2004
Slide 135
Elsmar.com --- The
Cove!
8-Disciplines Problem Solving
Elsmar.com
Interpreting Control Charts
Control Charts provide information as to whether a
process is being influenced by Chance causes or Special causes. A process
is said to be in Statistical Control when
all Special causes of variation have been removed and only Common causes remain. This is evidenced on a Control Chart by the absence of points beyond the Control Limits and by the absence
of Non-Random Patterns or Trends
within the Control
Limits. A process in Statistical Control
indicates that production is representative of
the best the process can achieve with the materials, tools and equipment provided. Further process improvement can only
be made by reducing variation due to Common
causes, which generally means management taking action to improve the system.
A. Most points are near the center
line.
B. A few points are near the control
limit.
C. No points (or only a ‘rare’ point)
are beyond the Control Limits.
Upper Control Limit
Lower Control Limit
Average