Chapter 4
Six Sigma for Process and
Quality Improvement
Chapter 4: Six Sigma for Process and Quality
Improvement
1
Quality Management and Six
Sigma in Perspective

Two primary sets of costs are involved
in quality:



control costs
failure costs
Costs broken into four categories:




Prevention costs
Appraisal costs
Internal costs of defects
External costs of defects
Chapter 4: Six Sigma for Process and Quality
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Japanese Approaches to Quality

In 1950 the Japanese government
invited W. Edwards Deming (then a
professor at New York University) to
give a series of lectures on quality
control to help Japanese engineers
reindustrialize the country.
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3
W. Edwards Deming



Major source of poor quality is
variation
Quality improvement the responsibility
of top management
All employees should be trained in use
of problem solving tools and especially
statistical techniques
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4
Deming’s 14 Points
1.
2.
3.
4.
Create constancy of purpose
Adopt the new philosophy
Cease dependence on mass inspection
End practice of awarding business on
basis of price tags
5. Improve constantly and forever
6. Institute modern methods of training
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5
Deming’s 14 Points continued
7. Institute modern method of
supervision
8. Drive out fear
9. Breakdown organizational barriers
10. Eliminate arbitrary numerical goals
11. Eliminate work standards and quotas
12. Remove barriers that reduce pride of
workmanship
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6
Deming’s 14 Points continued
13. Institute a vigorous program of
education and training
14. Push the 13 points everyday
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7
Total Quality Management (TQM)


Better to produce item right the first
time than to try to inspect quality in
Quality at the source - responsibility
shifted from quality control department
to workers
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8
History of TQM




Dr. Shewart began using statistical
control at the Bell Institute in 1930s
Military standards developed in 1950s
After World War II, Japanese Union of
Scientist and Engineers began
consulting with Deming
Deming Prize introduced in Japan in
1951
Chapter 4: Six Sigma for Process and Quality
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History of TQM continued
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Quality assurance concept proposed in 1952
Juran makes first trip to Japan in 1954
Quality becomes Japan’s national slogan in
1956
First quality circles created in 1957
10,000 quality circles by 1966
100,000 quality circles by 1977
First U.S. quality circle 1974
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Five Steps in TQM

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Determine what customers want
Develop products and services
Develop production system
Monitor the system
Include customers and suppliers
Chapter 4: Six Sigma for Process and Quality
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Joseph Juran



Quality Control Handbook (1951)
Employees speak in different languages
Quality Trilogy




Quality Planning
Quality Control
Quality Improvement
Need to place more emphasis on
planning and improvement
Chapter 4: Six Sigma for Process and Quality
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12
Joseph Juran continued

Organizations progress through four
phases




Minimize prevention and appraisal costs
Appraisal costs increased
Process control introduced increasing
appraisal costs but lowering internal and
external failure costs
Prevention costs increased in effort to
lower total quality costs
Chapter 4: Six Sigma for Process and Quality
Improvement
13
A Brief History of Six Sigma



The Six Sigma concept was developed by
Bill Smith, a senior engineer at Motorola, in
1986 as a way to standardize the way
defects were tallied.
Sigma is the Greek symbol used in statistics
to refer to standard deviation which is a
measure of variation.
Adding “six” to “sigma” combines a measure
of process performance (sigma) with the
goal of nearly perfect quality (six).
Chapter 4: Six Sigma for Process and Quality
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14
A Brief History of Six Sigma
continued

In the popular book The Six Sigma Way,
Six Sigma is defined as:

a comprehensive and flexible system for
achieving, sustaining and maximizing
business success. Six Sigma is uniquely
driven by close understanding of customer
needs, disciplined use of facts, data, and
statistical analysis, and diligent attention to
managing, improving, and reinventing
business processes. (p. xi)
Chapter 4: Six Sigma for Process and Quality
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15
The DMAIC Improvement Process

Six Sigma projects generally follow a
well defined process consisting of five
phases.
define
 measure
 analyze
 improve
 control
pronounced dey-MAY-ihk

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The DMAIC Improvement Process
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Chapter 4: Six Sigma for Process
and Quality Improvement
18
The Define Phase

The define phase of a DMAIC project focuses
on clearly specifying the problem or
opportunity, what the goals are for the
process improvement project, and what the
scope of the project is. Identifying who the
customer is and their requirements is also
critical given that the overarching goal for all
Six Sigma projects is improving the
organization’s ability to meet the needs of its
customers.
Chapter 4: Six Sigma for Process and Quality
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Defining and Measuring Quality





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


Conformance to specifications
Performance
Quick response
Quick-change expertise
Features
Reliability
Durability
Serviceability
Aesthetics
Perceived quality
Humanity
Value
Chapter 4: Six Sigma for Process and Quality
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Benchmarking

Benchmarking involves comparing an
organization's processes with the best
practices to be found. Benchmarking is
used for a variety of purposes, including:


Comparing an organization's processes
with the best organization's processes.
Comparing an organization's products and
services with those of other organizations.
Chapter 4: Six Sigma for Process and Quality
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Benchmarking continued


Identifying the best practices to
implement.
Projecting trends in order to be able to
respond proactively to future
challenges and opportunities.
Chapter 4: Six Sigma for Process and Quality
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Quality Function Deployment (QFD)


Two key drivers of an organization’s longterm competitive success are the extent to
which its new products or services meet
customers’ needs, and having the
organizational capabilities to develop and
deliver such new products and services.
Tools for helping translate customer desires
directly into product service attributes.
Chapter 4: Six Sigma for Process and Quality
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Four Houses of Quality




Customer requirements
Technical requirements
Component requirements
Process deployment requirements
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House of Quality Details
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The Measure Phase



The measure phase begins with the
identification of the key process performance
metrics.
Once the key process performance metrics
have been specified, related process and
customer data is collected.
Two commonly used process performance
measures, namely, Defects per Million
Opportunities (DPMO) and Process Sigma.
Chapter 4: Six Sigma for Process and Quality
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26
Defects Per Million Opportunities

Earlier it was noted that a literal
interpretation of Six Sigma is 3.4
defects per million opportunities
(DPMO). This may have caused some
confusion for more statistically inclined
readers, which we shall now attempt to
reconcile.
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27
Defects Per Million Opportunities
Chapter 4: Six Sigma for Process and Quality
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28
Process Sigma

How sigma itself can be used to
measure the performance of a
process.

One way to measure the performance of
a process is to calculate the number of
standard deviations the customer
requirements are from the process mean
or target value.
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DPMO for Alternative Process Sigma Levels
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Motorola’s Assumption the Process Mean Can
Shift by as Much as 1.5 Standard Deviations
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Comparison of 3 Sigma Process and 6 Sigma Process
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The Analyze Phase


In this phase our objective is to utilize
the data that has been collected to
develop and test theories related to the
root causes of existing gaps between
the process’ current performance and
its desired performance.
See next slide Table 4.3 Common
tools and methodologies in the Six
Sigma toolset.
Chapter 4: Six Sigma for Process and Quality
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33
Brainstorming

The brainstorming approach:




Do not criticize ideas during the
brainstorming session.
Express all ideas no matter how radical,
bizarre, unconventional, ridiculous, or
impractical they may seem.
Generate as many ideas as possible.
Combine, extend, and/or improve on one
another’s ideas.
Chapter 4: Six Sigma for Process and Quality
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Brainstorming: Actions to Enhance
Team Creativity

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







Create diversified teams.
Use analogical reasoning.
Use brain writing.
Use the Nominal Group Technique.
Record team ideas.
Use trained facilitators to run the brainstorming
session.
Set high standards.
Change the composition of the team.
Use electronic brainstorming.
Make the workplace a playground.
Chapter 4: Six Sigma for Process and Quality
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Cause and Effect Diagrams
Chapter 4: Six Sigma for Process and Quality
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Process Capability Analysis
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Improvement
37
Process Capability Analysis
continued
Chapter 4: Six Sigma for Process and Quality
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38
The Improve Phase: Design of
Experiments (DOE)

OFAT and 1FAT - one factor at a time.

Shortcomings


Not typically possible to test one factor at a
time and hold all the other factors constant.
Not possible to account for interactions or
joint variation between variables (Figure
4.16).
Chapter 4: Six Sigma for Process and Quality
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39
Design of Experiments (DOE)
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40
DOE: continued
Chapter 4: Six Sigma for Process and Quality
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41
DOE: continued
Chapter 4: Six Sigma for Process and Quality
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42
DOE continued

Some of the major considerations
associated with DOE include:




Determining which factors to include in
the experiment.
Specifying the levels for each factor.
Determining how much data to collect.
Determining the type of experimental
design.
Chapter 4: Six Sigma for Process and Quality
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43
Taguchi Methods


Design for Manufacturability (DFM)
Procedure for statistical testing to
determine best combination of product
and transformation system design that
will make output relatively independent
of normal fluctuations in the production
system
Chapter 4: Six Sigma for Process and Quality
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Statistical Quality Control
Chapter 4: Six Sigma for Process and Quality
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45
Chance Versus Assignable Variation



Chance variation is variability built into
the system.
Assignable variation occurs because
some element of the system or some
operating condition is out of control.
Quality control seeks to identify when
assignable variation is present so that
corrective action can be taken.
Chapter 4: Six Sigma for Process and Quality
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Control Based on Attributes and
Variables


Inspection for Variables: measuring a
variable that can be scaled such as
weight, length, temperature, and
diameter.
Inspection of Attributes: determining
the existence of a characteristic such as
acceptable-defective, timely-late, and
right-wrong.
Chapter 4: Six Sigma for Process and Quality
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Control Charts
Chapter 4: Six Sigma for Process and Quality
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48
Control Charts

Developed in 1920s to distinguish
between chance variation in a system
and variation caused by the system’s
being out of control - assignable
variation.
Chapter 4: Six Sigma for Process and Quality
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Control Charts continued




Repetitive operation will not produce
exactly the same outputs.
Pattern of variability often described by
normal distribution.
Random samples that fully represent the
population being checked are taken.
Sample data plotted on control charts to
determine if the process is still under
control.
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Control Chart with Limits Set at Three Standard
Deviations
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Control Charts for Variables
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Two Control Charts


Sample Means Chart
Range Chart
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Sample Data of Weights of Tacos
(Ounces)
S a m p le
S cen a rio 1
S cen a rio 2
1
4, 5, 6
4, 5, 6
2
6, 7, 8
3, 5, 7
3
7, 8, 9
2, 5, 8
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Analysis of Scenario 1
S a m p le
M ea n
R ange
1
5
2
2
7
2
3
8
2
Sample means show problem having increased from 5
ounces to 8 ounces. Sample ranges have not changed
from sample to sample.
Chapter 4: Six Sigma for Process and Quality
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55
Analysis of Scenario 2
S a m p le
M ea n
R ange
1
5
2
2
5
4
3
5
6
Sample ranges show problem having increased from 2
ounces to 6 ounces. Sample means have not changed
from sample to sample.
Chapter 4: Six Sigma for Process and Quality
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Patterns of Change in Process Distributions
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57
Control Limits
Sample Means Chart:
UCL
LCL
X
X
 X  A2R
 X  A2R
Range Chart:
UCL
R
 D4R
LCL
R
 D3R
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Calculating the Grand Mean and the
Average Range
X 
X
N
R 
R
N
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Mean Age of Ice Cream
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Range in Ice Cream Age
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Control Charts for Attributes
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Fraction-Defective (p) Charts
total number
p
total number

p
of defects
of units sampled
p (1  p )

n
UCL
p
 p  z
LCL
p
 p  z
p
p
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Number-of-Defects (c) Charts
c
number
of incidents
number
c 
observed
of units sampled
c
UCL
c
 c  z c
LCL
c
 c  z c
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Six Sigma in Practice

Six Sigma Roles:





Master Black Belts.
Black Belts.
Green Belts.
Yellow Belts.
Supporting Roles:


Champions/Sponsors.
Process owners.
Chapter 4: Six Sigma for Process and Quality
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65
Quality in Services




Measuring is difficult
Training in standard procedures often
used to improve quality
One way to measure quality of services
is to use customer satisfaction surveys
J.D. Power and Associates uses
surveys to rate domestic airlines, hotel
chains, and rental car companies.
Chapter 4: Six Sigma for Process and Quality
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Rating the Performance of Domestic
Airlines




On-time performance (25%)
Airport check-in (11%)
Courtesy of flight attendants (11%)
Seating comfort (11%)
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Service Defections

Organizations should monitor
customer defections



feedback from defecting customers can
be used to identify problem areas
can determine what is needed to win
them back
changes in defection rate can be used as
early warning signal
Chapter 4: Six Sigma for Process and Quality
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Quality Awards/Certifications
Chapter 4: Six Sigma for Process and Quality
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69
The Malcolm Baldrige National Quality
Award
Chapter 4: Six Sigma for Process and Quality
Improvement
70
ISO 9000


Guidelines for designing,
manufacturing, selling, and servicing
products.
Selecting an ISO 9000 certified
supplier provides some assurance that
supplier follows accepted business
practices in areas covered by the
standard
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Elements of ISO 9000

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Management Responsibility
Quality System
Contract Review
Design Control
Document and Data Control
Purchasing
Control of Customer Supplied
Product
Product Identification and Traceability
Process Control
Inspection and Testing









Control of Inspection,
Measuring, and Test
Equipment
Inspection and Test Status
Control of Nonconforming
Product
Corrective and Preventive
Action
Handling, Storage,
Packaging, Preservation, and
Delivery
Internal Quality Audits
Training
Servicing
Statistical Techniques
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Chapter 4: Six Sigma for Process
and Quality Improvement
73
ISO 14000


Series of standards covering environmental
management systems, environmental
auditing, evaluation of environmental
performance, environmental labeling, and
life-cycle assessment.
Intent is to help organizations improve their
environmental performance through
documentation control, operational control,
control of records, training, statistical
techniques, and corrective and preventive
actions.
Chapter 4: Six Sigma for Process and Quality
Improvement
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Chapter 4: Six Sigma for Process
and Quality Improvement
75
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Chapter 4: Six Sigma for Process and Quality
Improvement
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