Statistical Quality Control

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Statistical Quality Control Sixth Edition

Eugene L. Grant

Professor of Economics of Engineering, Emeritus Stanford University

Richard S. Leavenworth Professor of Industrial and Systems Engineering University of Florida

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McGraw-Hill Book Company New York St. Louis San Francisco Auckland Bogota Caracas Colorado Springs Hamburg Lisbon London Madrid Mexico Milan Montreal New Delhi Oklahoma City Panama Paris San Juan Säo Paulo Singapore Sydney Tokyo Toronto

Contents List of Examples Preface

1

xv

Introduction

Part One

xiii

1

Statistical Process Control

29

2

Why the Control Chart Works; Some Statistical Concepts frequency distributions; averages and measures of dispersion; statistics and parameters; normal curve; estimating parameters 31

3

Why the Control Chart Works; Some Examples control-chart limit factors; Shewhart's normal bowl; lack of control; interpreting patterns of variation 74

4

Directions for Simple X and R Charts control-chart objectives; subgrouping; recording measurements; plotting control charts; drawing conclusions; revising control limits; use of computer software 115

5

Rational Subgrouping; Analyzing Process Capability sources of variation; isolating variation sources; using control charts to analyze variation; process capability indexes; other statistical techniques 154

6

Some Fundamentals of the Theory of Probability definitions and concepts; basic theorems; hypergeometric, binomial, and Poisson distributions; normal distribution and Central Limit Theorem; estimating parameters; extreme runs; computer programs 181

7

The Control Chart for Fraction Rejected p chart; trial limits; standard

X

Contents

values; revising control limits; steps for control-chart setup; np chart; interpretation of lack of control 239 8

The Control Chart for Nonconformities с chart; и chart; probability limits; Pareto Analysis; Cause and Effect Analysis; weighting nonconformities 274

9

Some Special Process Control Procedures variations on the standard Shewhart chart; charts for medians; homogeneity tests; probability limits; charts for moving averages; linear trend charts; narrow limit gauging; reject limits; acceptance control charts 302

10

Cumulative Sum Control Charts X chart and mask construction; Average Run Length; R chart mask construction 348

11

Some Aspects of Specifications and Tolerances setting design specifications; interpreting pilot runs; combinations of tolerances; measurement error 361

Part Two

Acceptance Sampling

391

12

Some Fundamental Concepts in Acceptance Sampling operating characteristic curves; distribution assumptions; indexing systems of acceptance plans; single-, double-, and multi-level plans 393

13

The Dodge-Romig System for Lot-by-Lot Acceptance Sampling by Attributes indexing plans by Lot Tolerance Percent Defective and Average Outgoing Quality Limit; calculation of AOQ; Average Fraction Inspected; plan operation; minimizing total inspection 426

14

An AQL System for Lot-by-Lot Acceptance Sampling by Attributes (ABC-STD-105) indexing by Acceptable Quality Level (AQL); operation of a system of plans; plan ОС curves vs. system ОС curves; Average Sample Number (ASN); classification of defects; Limiting Quality (LQ); ANSI standard Z 1.4 450

15

Certain Other Plans for Lot-by-Lot Acceptance Sampling by Attributes custom sampling plans; sequential sampling; Philips Standard Sampling System; a simplified AQL system; chain sampling 492

16

Acceptance Inspection for Continuous Production continuous sampling plans CSP-1, CSP-2, and CSP-3; multilevel continuous sampling; skip-lot sampling Plans SkSP-1 and SkSP-2 520

17

Acceptance Sampling by Variables Lot Plot method; ОС curves for known o- variables sampling plans; MIL-STD-414 system of plans, known and unknown о-; ANSI standard Z1.9; proof testing 537

18

Some Aspects of Life Testing and Reliability relationship of life testing to acceptance sampling; constant failure rate assumption; ОС curves;

Contents

estimating mean life; government publications; reliability functions other than negative exponential 580

Part Three

Some Related Topics

613

19

Some Economic Aspects of Quality Decisions

20

Demonstrating the Operation of Systems of Chance Causes

21

The Widespread Usefulness of Control Charts and Acceptance Sampling Procedures 640

Appendixes

2 Bibliography

A В С D E F G H J К L M N О P Q

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646

1 Glossary of Symbols

3 Tables

615

646

656

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Area under the normal curve 666 Right tail area of the \2 distribution 668 Factors for estimating a from R, J, orCTRMSand aR from R . _669 Factors for determining from R the 3-sigma control limits for X and R charts 670 Factors for determining from J and crRMs the 3-sigma control limits for X and s or aRMS charts 671 Factors for determining from a the 3-sigma control limits for X, R, and л or