Contents

Cover

Half Title page

Title page

Copyright page

Dedication

Preface

Changes in the Third Edition

Acknowledgments

Part I: Philosophy and Fundamentals

Chapter 1: Introduction to Quality Control and the Total Quality System

1-1 Introduction and Chapter Objectives

1-2 Evolution of Quality Control

1-3 Quality

1-4 Quality Control

1-5 Quality Assurance

1-6 Quality Circles and Quality Improvement Teams

1-7 Customer Needs and Market Share

1-8 Benefits of Quality Control and the Total Quality System

1-9 Quality and Reliability

1-10 Quality Improvement

1-11 Product and Service Costing

1-12 Quality Costs

1-13 Measuring Quality Costs

1-14 Management of Quality

1-15 Quality and Productivity

1-16 Total Quality Environmental Management

1-17 Profile of a Company: The Bama Companies, Inc.

Summary

Key Terms

Exercises

References

Chapter 2: Some Philosophies and Their Impact on Quality

2-1 Introduction and Chapter Objectives

2-2 Service Industries and Their Characteristics

2-3 Model for Service Quality

2-4 W. Edwards Deming’s Philosophy

2-5 Philip B. Crosby’s Philosophy

2-6 Joseph M. Juran’s Philosophy

2-7 the Three Philosophies Compared

Summary

Case Study: Clarke American Checks, Inc.

Key Terms

Exercises

References

Chapter 3: Quality Management: Practices, Tools, and Standards

3-1 Introduction and Chapter Objectives

3-2 Management Practices

3-3 Quality Function Deployment

3-4 Benchmarking and Performance Evaluation

3-5 Tools for Continuous Quality Improvement

3-6 International Standards ISO 9000 and Other Derivatives

3-7 Malcolm Baldrige National Quality Award

Summary

Case Study: Robert Wood Johnson University Hospital Hamilton

Key Terms

Exercises

References

Part II: Statistical Foundations and Methods of Quality Improvement

Chapter 4: Fundamentals of Statistical Concepts and Techniques in Quality Control and Improvement

4-1 Introduction and Chapter Objectives

4-2 Population and Sample

4-3 Parameter and Statistic

4-4 Probability

4-5 Descriptive Statistics: Describing Product or Process Characteristics

4-6 Probability Distributions

4-7 Inferential Statistics: Drawing Conclusions on Product and Process Quality

Summary

Appendix: Approximations to Some Probability Distributions

Key Terms

Exercises

References

Chapter 5: Data Analyses and Sampling

5-1 Introduction and Chapter Objectives

5-2 Empirical Distribution Plots

5-3 Randomness of a Sequence

5-4 Validating Distributional Assumptions

5-5 Transformations to Achieve Normality

5-6 Analysis of Count Data

5-7 Concepts in Sampling

Summary

Key Terms

Exercises

References

Part III: Statistical Process Control

Chapter 6: Statistical Process Control Using Control Charts

6-1 Introduction and Chapter Objectives

6-2 Causes of Variation

6-3 Statistical Basis for Control Charts

6-4 Selection of Rational Samples

6-5 Analysis of Patterns in Control Charts

6-6 Maintenance of Control Charts

Summary

Key Terms

Exercises

References

Chapter 7: Control Charts for Variables

7-1 Introduction and Chapter Objectives

7-2 Selection of Characteristics for Investigation

7-3 Preliminary Decisions

7-4 Control Charts for the Mean and Range

7-5 Control Charts for the Mean and Standard Deviation

7-6 Control Charts for Individual Units

7-7 Control Charts for Short Production Runs

7-8 Other Control Charts

7-9 Multivariate Control Charts

Summary

Key Terms

Exercises

References

Chapter 8: Control Charts for Attributes

8-1 Introduction and Chapter Objectives

8-2 Advantages and Disadvantages of Attribute Charts

8-3 Preliminary Decisions

8-4 Chart for Proportion Nonconforming: p-Chart

8-5 Chart for Number of Nonconforming Items: np-Chart

8-6 Chart for the Number of Nonconformities: c-Chart

8-7 Chart for Number of Nonconformities Per Unit: u-Chart

8-8 Chart for Demerits Per Unit: U-Chart

8-9 Charts for Highly Conforming Processes

8-10 Operating Characteristic Curves for Attribute Control Charts

Summary

Key Terms

Exercises

References

Chapter 9: Process Capability Analysis

9-1 Introduction and Chapter Objectives

9-2 Specification Limits and Control Limits

9-3 Process Capability Analysis

9-4 Natural Tolerance Limits

9-5 Specifications and Process Capability

9-6 Process Capability Indices

9-7 Process Capability Analysis Procedures

9-8 Capability Analysis for Nonnormal Distributions

9-9 Setting Tolerances on Assemblies and Components

9-10 Estimating Statistical Tolerance Limits of a Process

Summary

Key Terms

Exercises

References

Part IV: Acceptance Sampling

Chapter 10: Acceptance Sampling Plans for Attributes and Variables

10-1 Introduction and Chapter Objectives

10-2 Advantages and Disadvantages of Sampling

10-3 Producer and Consumer Risks

10-4 Operating Characteristic Curve

10-5 Types of Sampling Plans

10-6 Evaluating Sampling Plans

10-7 Bayes’ Rule and Decision Making Based on Samples

10-8 Lot-by-Lot Attribute Sampling Plans

10-9 Other Attribute Sampling Plans

10-10 Deming’s kp Rule

10-11 Sampling Plans for Variables

10-12 Variable Sampling Plans for a Process Parameter

10-13 Variable Sampling Plans for Estimating the Lot Proportion Nonconforming

Summary

Key Terms

Exercises

References

Part V: Product and Process Design

Chapter 11: Reliability

11-1 Introduction and Chapter Objectives

11-2 Reliability

11-3 Life-Cycle Curve and Probability Distributions in Modeling Reliability

11-4 System Reliability

11-5 Operating Characteristic Curves

11-6 Reliability and Life Testing Plans

Summary

Key Terms

Exercises

References

Chapter 12: Experimental Design and the Taguchi Method

12-1 Introduction and Chapter Objectives

12-2 Experimental Design Fundamentals

12-3 Some Experimental Designs

12-4 Factorial Experiments

12-5 The Taguchi Method

12-6 The Taguchi Philosophy

12-7 Loss Functions

12-8 Signal-to-Noise Ratio and Performance Measures

12-9 Critique of S/N Ratios

12-10 Experimental Design in the Taguchi Method

12-11 Parameter Design in the Taguchi Method

12-12 Critique of Experimental Design and the Taguchi Method

Summary

Key Terms

Exercises

References

Appendixes

Appendix A-1 Cumulative Binomial Distribution

Appendix A-2 Cumulative Poisson Distribution

Appendix A-3 Cumulative Standard Normal Distribution

Appendix A-4 Values of t for a Specified Right-Tail Area

Appendix A-5 Chi-Squared Values for a Specified Right-Tail Area

Appendix A-6 Values of F for a Specified Right-Tail Area

Appendix A-7 Factors for Computing Center line and Three-Sigma Control Limits

Appendix A-8 Uniform Random Numbers

Index

FUNDAMENTALS OF QUALITY CONTROL AND IMPROVEMENT

Copyright © 2008 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey.
Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

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Library of Congress Cataloging-in-Publication Data:

Mitra, Amitava.
Fundamentals of quality control and improvement / Amitava Mitra. – 3rd ed.
p. cm.
Includes index.
ISBN 978-0-470-22653-7 (cloth)
1. Quality control – Statistical methods. I. Title.
TS156 . M54 2008
658.4’0.13–dc22
2007036433

To the memory of my father, and my mother, who instilled the importance of an incessant inquiry for knowledge — and whose inspiration transcends mortality

PREFACE

This book covers the foundations of modern methods of quality conrol and improvement that are used in the manufacturing and service industries. Quality is key to surviving tough competition. Consequently, business needs technically competent people who are well-versed in statistical quality control and improvement. This book should serve the needs of students in business and management and students in engineering, technology, and related disciplines. Professionals will find this book to be a valuable reference in the field.

An outgrowth of many years of teaching, research, and consulting in the field of quality assurance and statistical process control, the methods discussed in this book apply statistical foundations to real-world situations. Mathematical derivations and proofs are kept to a minimum to allow a better flow of material. Although an introductory course in statistics would be useful to a reader, the foundations of statistical tools and techniques discussed in Chapter 4 should enable students without a statistical background to understand the material.

Prominently featured are many real-world examples. For each major concept, at least one example demonstrates its application. Furthermore, case studies at the end of some chapters enhance student understanding of pertinent issues.

The book is divided into five parts. Part I, which deals with the philosophy and fundamentals of quality control, consists of three chapters. Chapter 1 is an introduction to quality control and the total quality system. In addition to introducing the reader to the nomenclature associated with quality control and improvement, it provides a framework for the systems approach to quality. Discussions of quality costs and their measurement, along with activity-based costing, are presented. In Chapter 2 we examine philosophies of such leading experts as Deming, Crosby, and Juran. Deming’s 14 points for management are analyzed, and the three philosophies are compared. Features of quality in the service sector are introduced. Chapter 3 covers quality management practices, tools, and standards. Topics such as total quality management, balanced scorecard, quality function deployment, benchmarking, failure mode and effects criticality analysis, and tools for quality improvement are presented. We also discuss the criteria for the Malcolm Baldrige National Quality Award in the United States and the International Organization for Standardization (ISO) 9000 standards.

Part II deals with the statistical foundations of quality control and consists of two chapters. Chapter 4 offers a detailed coverage of statistical concepts and techniques in quality control and improvement. It present a thorough treatment of inferential statistics. Depending on the student’s background, only selected sections of this chapter will need to be covered.

Chapter 5 covers some graphical methods of empirical distributions. Identification of the population distribution using probability plotting along with the several transformations to achieve normality are presented. Analysis of count data, including contingency table analysis and measures of association, are discussed. Finally, some common sampling designs and determination of an appropriate sample size are features of this chapter.

The field of statistical quality control consists of two areas: statistical process control and acceptance sampling. Part III deals with statistical process control and consists of four chapters. Chapter 6 provides an overview of the principles and use of control charts. A variety of control charts for variables are discussed in detail in Chapter 7. In additon to charts for the mean and range, those for the mean and standard deviation, individual units, cumulative sum, moving average, geometric moving average, and trends are presented. Control charts for attributes are discussed in Chapter 8. Charts such as the p-chart, np-chart, c-chart, u-chart, and U-chart are presented. The topic of process capability analysis is discussed in Chapter 9. The ability of a process to meet customer specifications is examined in detail. Process capability analysis procedures and process capability indices are also treated in depth. The chapter covers proper approaches to setting tolerances on assemblies and components. Part III should form a core of material to be covered in most courses.

Part IV deals with acceptance sampling procedures and cosists of one chapter. Methods of acceptance of a product based on information from a sample are described. Chapter 10 presents acceptance sampling plans for attributes and variables. Lot-by-lot attribute and variable sampling plans are described. With the emphasis on process control and improvement, sampling plans do not occupy the forefront. Nevertheless, they are included to make the discussion complete.

Part V deals with product and process design and consists of two chapters. With the understanding that quality improvement efforts are generally being moved further upstream, these chapters constitute the backbone of current methodology. Chapter 11 deals with reliability and explores the effects of time on the proper functioning of a product. Chapter 12 provides the fundamentals of experimentals design and the Taguchi method. Different designs, such as the completely randomized design, randomized block design, and Latin square design are presented. Estimation of treatment effects using factorial experiments is included. This chapter also provides a treatment of the Taguchi method for design and quality improvement; the philosophy and fundamentals of this method are discussed. Various sections of Part V could also be included in the core material for a quality control course.

This book may serve as a text for an undergraduate or graduate course for students in business and management. It may also serve the needs of students in engineering, technology, and related disciplines. For a one-semester or one-quarter course, Part I, selected portions of Part II, selected portions of Part III, and selected portions of Part V could be covered. For a two-semester or two-quarter course, all of Parts II, III, and V, along with portions from Part IV, could be covered as well.

CHANGES IN THE THIRD EDITION

Some major changes have been made in the third edition. First, the theme of applications of quality control and improvement in the service sector has been integrated throughout the book. Second, the use of a computer software package, Minitab, is demonstrated. Third, new case studies are introduced in some of the chapters. Some of the initial chapters also include profiles of Malcolm Baldrige National Quality Award winners that demonstrate best-business practices and their performance achievements. Fourth, many of the chapter-end exercises have been revised. Fifth, some new material has been included in appropriate chapters as discussed below.

Chapter 1 has been revamped completely. Concepts and applications of activity-based costing are included. The discussion of quality costs and the impact of various factors, such as product development, have been expanded. The effects of first-pass yield and inspection on unit costs are elaborated. Chapter 2 now includes a discussion of the unique characteristics of a model for quality in the service sector. Ideas on the balanced scorecard and failure mode effects and criticality analysis have been added to Chapter 3. Multivariable charts, matrix plots, and surface plots are included as part of the tools for quality improvement. The gamma and lognormal distributions as well as the paired-difference t-test are now discussed in Chapter 4. Chapter 5 has been modified intensively to include validation of distributional assumptions, since many statistical tests and inferences are based on a population distributional assumptions. Special attention is devoted to transformations to achieve normality. Expanded coverage of sampling and sample size determination are now featured. Analysis of count data is an added section. Control charts for short production runs and added discussion of multivariate control charts, including the generalized variance chart, are part of Chapter 7.

A section on control charts for highly conforming processes is now included in Chapter 8. Some new process capability measures, Cpmk and Cpq, along with making inferences on capability indices, are included in Chapter 9. The discussion on gage repeatability and reproducibility has been expanded, with capability analysis for nonnormal distributions being featured. Setting tolerances on nonlinear combinations of random variables are part of Chapter 9. The use of Bayes’ rule in updating prior probabilities and the use of sample information to make optimal decisions are illustrated in Chapter 10. A brief discussion of availability is now provided in Chapter 11. Finally, accumulation analysis using attribute data is discussed in Chapter 12.

ACKNOWLEDGMENTS

Many people have contributed to the development this book, and thanks are due to them. Modern trends in product/process quality through design and improvement, as well as discussions and questions from undergraduate and graduate classes over the years, have shaped this book. Applications encountered in a consulting environment have provided a scenario for examples and exercises. Input from faculty and professional colleagues, here and abroad, has facilitated composition of the material. Constructive comments from the reviewers have been quite helpful. Many of the changes in the third edition are based on input from those who have used the book as well as from reviewers.

The manuscript preparation center of the College of Business at Auburn University did a remarkable job for which Margie Maddox is to be congratulated. I would like to thank Minitab, Inc. (Quality Plaza, 1829 Pine Hall Road, State College, PA 16801-3008) for its assistance in providing software support. My editor, Steve Quigley, is to be commended for his patience and understanding.

Learning is a never-ending process. It takes time and a lot of effort. So does writing and revising a book. That has been my reasoning to my wife, Sujata, and son, Arnab. I believe they understand this—my appreciation to them. Their continual support has provided an endless source of motivation.

PART I

PHILOSOPHY AND FUNDAMENTALS

CHAPTER 1

INTRODUCTION TO QUALITY CONTROL AND THE TOTAL QUALITY SYSTEM

1-1 Introduction and chapter objectives

1-2 Evolution of quality control

1-3 Quality

1-4 Quality control

1-5 Quality assurance

1-6 Quality circles and quality improvement teams

1-7 Customer needs and market share

1-8 Benefits of quality control and the total quality system

1-9 Quality and reliability

1-10 Quality improvement

1-11 Product and service costing

1-12 Quality costs

1-13 Measuring quality costs

1-14 Management of quality

1-15 Quality and productivity

1-16 Total quality environmental management

1-17 Profile of a company: The Bama Companies, Inc.

Summary

1-1 INTRODUCTION AND CHAPTER OBJECTIVES

Wa…ah, Wa…ah, Wa…ah. It was about 2 A.M. The resident physician had just delivered the newborn and the proud parents were ecstatic. Forgotten in an instant, as she held the infant close to her, was the pain and suffering of the mother. “Wouldn’t it be nice if one could share this moment, right now, with family and loved ones who are far away?”, thought the parents. As if through extrasensory perception, the physician understood this desire. In a moment, the digital camera that was already in place started streaming the video to the cell phones and Web addresses of those designated. Now, both parties could hear and see each other as they shared this unique and rare moment in a bond of togetherness. The developments of the twenty-first century and the advances in quality make this possible.

The objectives of this chapter are, first, to define quality as it relates to the manufacturing and service sector, to introduce the terminology related to quality, and to set up a framework for the design and implementation of quality. Of importance will be the ability to identify the unique needs of the customer, which will assist in maintaining and growing market share. A study of activity-based product costing will be introduced along with the impact of quality improvement on various quality-related costs. The reader should be able to interpret the relationships among quality, productivity, long-term growth, and customer satisfaction.

1-2 EVOLUTION OF QUALITY CONTROL

The quality of goods produced and services rendered has been monitored, either directly or indirectly, since time immemorial. However, using a quantitative base involving statistical principles to control quality is a modern concept.

The ancient Egyptians demonstrated a commitment to quality in the construction of their pyramids. The Greeks set high standards in arts and crafts. The quality of Greek architecture of the fifth century B.C. was so envied that it profoundly affected the subsequent architectural constructions of Rome. Roman-built cities, churches, bridges, and roads inspire us even today.

During the Middle Ages and up to the nineteenth century, the production of goods and services was confined predominantly to a single person or a small group. The groups were often family-owned businesses, so the responsibility for controlling the quality of a product or service lay with that person or small group—Those also responsible for producing items conforming to those standards. This phase, comprising the time period up to 1900, has been labeled by Feigenbaum (1983) the operator quality control period. The entire product was manufactured by one person or by a very small group of persons. For this reason, the quality of the product could essentially be controlled by a person who was also the operator, and the volume of production was limited. The worker felt a sense of accomplishment, which lifted morale and motivated the worker to new heights of excellence. Controlling the quality of the product was thus embedded in the philosophy of the worker because pride in workmanship was widespread.

Starting in the early twentieth century and continuing to about 1920, a second phase evolved, called the foreman quality control period (Feigenbaum 1983). With the Industrial Revolution came the concept of mass production, which was based on the principle of specialization of labor. A person was responsible not for production of an entire product but rather, for only a portion of it. One drawback of this approach was the decrease in the workers’ sense of accomplishment and pride in their work. However, most tasks were still not very complicated, and workers became skilled at the particular operations that they performed. People who performed similar operations were grouped together. A supervisor who directed that operation now had the task of ensuring that quality was achieved. Foremen or supervisors controlled the quality of the product, and they were also responsible for operations in their span of control.

The period from about 1920 to 1940 saw the next phase in the evolution of quality control. Feigenbaum (1983) calls this the inspection quality control period. Products and processes became more complicated, and production volume increased. As the number of workers reporting to a foreman grew in number, it became impossible for the foreman to keep close watch over individual operations. Inspectors were therefore designated to check the quality of a product after certain operations. Standards were set, and inspectors compared the quality of the item produced against those standards. In the event of discrepancies between a standard and a product, deficient items were set aside from those that met the standard. The nonconforming items were reworked if feasible, or were discarded.

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