Control chart for Managers

Control Chart Workshop
for Management

http://www.gbna.ca

Learning Objectives

At the end of this workshop, you will be able
to:
Interpret your control chart
Explain the benefits of a control chart

Would you like to gain something else from
this session?

© 2012 Gilles Bélanger & Associates Inc. 2

The Origin of the
Control Charts
Control Charts were invented by Walter A Shewart while working for
Bell Labs in the 20’s.

• He developed a theory that there are two components to
variation:

• Common Cause: random and predictable
• Special Cause: non-random and assignable cause that could be
internal or external to the system

Over the next 50 years, Dr. W. Edwards Deming became the
biggest proponent of Shewart’s work.

• His definition of Special Cause is: non-random and unusual
event external to the system


Key Discussion Points

What is a control chart and what are its
components?
Why is the control chart important for me and
what is it telling me?

It provides a clear signal when management
intervention is required.


Shewhart’s contribution

Control chart illustrates process behavior over
time

It’s a special cause detection tool
Can also be used as a predictive tool when
the process is stable

Components of a
Control Chart

Upper and
Lower
Data Mean control Limit
is always are shown.
shown
They reflect
the Voice of
the
Process.


Components of a
Control Chart
Upper and
Lower
control
limits Upper Spec
represents limit defined
±3 by
standard management
deviations. or a third
Standard party.
deviation is
a measure
of variation.
The data in above control chart are within the control limits. The
process is stable and predictable. We can predict there is a 99.7%
probability the next data point will be between 4.13 and 5.95).

Components of a
Control Chart
Upper Control
Limit (ULC): 3σ

Lower Control
σ= SIGMA-Letter from the Greek alphabet used in Limit (LCL): -3σ
statistics as a symbol for standard deviation


Components of a
Control Chart
Mean

Lower Control Limit Upper Control Limit

Normal distribution (symmetrical) :
68% of data points are contained within ±1σ,
95% of data points are contained within ± 2 σ,
99.7% of data points are contained within ± 3 σ (UCL & LCL).

Components of a
Control Chart
When all data
points are
within the
Control Limits
we have
common
cause,
routine,
Normal random
distribution variation.

Special cause conditions are unusual, non-random events, external to the
system. When one or several data points are outside the Control Limits, the
process is Out of Control and management attention is required.


Components of a
Control Chart

What can you conclude about the profit goal?


Why is a Control Chart important for me?

1. Allows you to see patterns and trends over time
2. Make a distinction between special causes and common causes
of variation
3. May be used as a tool for ongoing control of process
4. Warns you when a problem or a shift in the process has
occurred
5. Provides a common language for discussing process
performance

Control chart is a tool that helps you to effectively monitor process
performance metrics and support you and your team in better
managing improved processes by validating their stability, predictability
and performance.

Why is a Control Chart important for me?

Customers may be
How your internal or external.
Customer feels
the process

Happy
Happy
employees! Stability Predictability
Customers!

Is your process stable
and predictable over
Control Chart time?


What is a Control Chart telling me?

Special cause: Special cause:
investigate, investigate
possible
temporary
process shift?
Common
cause: do
not react.

Control chart shows the “Voice of the Process” and tells you when to keep going
or stop and investigate for a special cause!


Upper and Lower Control Limits are determined by the process and not by
management or third party specifications


BEFORE After your
Before any
improvement team’s process
we have an improvement
average wait project, we can
time of 11 predict there is
minutes a 99.7%
probability the
next data point
AFTER will be between
6.89 and 11.19
minutes. New
average is 9
minutes!


Control Chart benefits
Summary

No more firefighting.
Better resource
React only to special
management!
causes that are outside
Happier employees! the Voice of the Process
Control Limits!

Higher quality of
work, no
surprises.


Questions?

Please email any question to: gbelanger@gbna.ca

Control chart for Managers

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