Root Cause Analysis The Core of Problem Solving and Corrective Action
Duke Okes
ASQ Quality Press Milwaukee, Wisconsin
American Society for Quality Quality,, Quality Press, Milwauk Milwaukee ee 53203 © 2009 by Duke Okes Published 2009 Printed in the United States of America
Library of Congress Cataloging-in-Publication Data
Okes, Duke, 1949–. Root cause analysis : the core of problem problem solving and corrective action / Duke Okes. p. cm. ISBN 978-0-87389-764-8 (alk. paper) 1. Problem solving. 2. Decision making. 3. Management. I. Tit Title. le. HD30.29.O44 2009 658.4’03—dc22
2008055044
American Society for Quality Quality,, Quality Press, Milwauk Milwaukee ee 53203 © 2009 by Duke Okes Published 2009 Printed in the United States of America
Library of Congress Cataloging-in-Publication Data
Okes, Duke, 1949–. Root cause analysis : the core of problem problem solving and corrective action / Duke Okes. p. cm. ISBN 978-0-87389-764-8 (alk. paper) 1. Problem solving. 2. Decision making. 3. Management. I. Tit Title. le. HD30.29.O44 2009 658.4’03—dc22
2008055044
Contents
List of Figur Figures es and Tables Tables . . . . . . . . . . . . . . . . . . . . . . . .
xi
Preface Pr eface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xv
Chapter 1
Getting Better Root Cause Analysis . . .
1
The Problem . . . . . . . . . . . . . . . . . . . . . . . The Impact . . . . . . . . . . . . . . . . . . . . . . . . Approaches Appro aches to Root Cause Analy Analysis sis . . . . Existing Problem-Solving Models . . . . . . A Proposed Model . . . . . . . . . . . . . . . . . .
2 3 4 6 7
Multiplee Causes and Types of Action . . . Multipl
13
Initial Problem Response . . . . . . . . . . . . . The Diagn Diagnosis osis . . . . . . . . . . . . . . . . . . . . . Actions Actio ns to Pre Prevent vent Futur Futuree Probl Problems ems . . . . The Need for Filters . . . . . . . . . . . . . . . . .
13 14 19 20
Step 1: Def Define ine the Problem . . . . . . . . . .
23
Selecting the Right Probl Selecting Problem em . . . . . . . . . . Scoping the Problem Appropriately . . . . . The Problem Statement . . . . . . . . . . . . . .
24 30 31
Chapterr 2 Chapte
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Step 2: Understand the Process . . . . . .
37
Setting Process Boundaries . . . . . . . . . . . Flowcharting the Process . . . . . . . . . . . . . Why Process Is So Important . . . . . . . . . . Additional Values of the Flowchart . . . . .
37 39 44 46
Step 3: Identify Possible Causes . . . . . .
49
Using the Flowchart for Causes . . . . . . . . Using a Logic Tree for Causes . . . . . . . . . Using Brainstorming and the Cause-andEffect Diagram for Causes . . . . . . . . . Using Barrier Analysis for Causes . . . . . . Using Change Analysis for Causes . . . . . Eliminating Possible Causes . . . . . . . . . . Sources for Possible Causes. . . . . . . . . . .
50 51 57 60 61 62 63
Step 4: Collect the Data . . . . . . . . . . . . .
65
A Basic Concept . . . . . . . . . . . . . . . . . . . Types of Data . . . . . . . . . . . . . . . . . . . . . . Using Existing versus New Data . . . . . . . Where to Collect Data . . . . . . . . . . . . . . . Special Tests . . . . . . . . . . . . . . . . . . . . . . . Sample Size and Time Frame . . . . . . . . . Data Collection Tools for Both Low- and High-Frequency Problems . . . . . . . . . Additional Tools for High-Frequency Problems . . . . . . . . . . . . . . . . . . . . . . Organizing the Data Collection Process .
66 67 69 69 71 74
79 80
Step 5: Analyze the Data . . . . . . . . . . . .
83
Tools for Low-Frequency Data . . . . . . . . Additional Tools for High-Frequency Data . . . . . . . . . . . . . . . . . . . . . . . . . .
84
75
86
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Questioning the Data . . . . . . . . . . . . . . . . Data Analyses Summaries . . . . . . . . . . . . Analyzing Variation . . . . . . . . . . . . . . . . . Where to Go Next? . . . . . . . . . . . . . . . . .
95 95 97 98
Identify and Select Solutions . . . . . . . . .
99
Step 6: Identify Possible Solutions . . . . . Step 7: Select Solution(s) to Be Implemented . . . . . . . . . . . . . . . . . . .
99 106
Implement, Evaluate, and Institutionalize . . . . . . . . . . . . . . . . . . . .
113
Step 8: Implement the Solution(s) . . . . . . Step 9: Evaluate the Effect(s). . . . . . . . . . Step 10: Institutionalize the Change . . . .
113 115 117
Organizational Issues. . . . . . . . . . . . . . .
119
Cognitive Biases . . . . . . . . . . . . . . . . . . . Resistance to Change . . . . . . . . . . . . . . . . Organizational Culture . . . . . . . . . . . . . . . Project Ownership . . . . . . . . . . . . . . . . . . Coaching/Facilitation Skills . . . . . . . . . . . Other Issues . . . . . . . . . . . . . . . . . . . . . . .
119 121 125 126 126 131
Human Error and Incident Analysis . .
133
Human Error . . . . . . . . . . . . . . . . . . . . . . Incident Analysis . . . . . . . . . . . . . . . . . . .
133 139
Improving Corrective Action . . . . . . . .
143
Critical Thinking . . . . . . . . . . . . . . . . . . . Buddhism . . . . . . . . . . . . . . . . . . . . . . . . . Stoic Philosophy . . . . . . . . . . . . . . . . . . . Summary of Root Cause Analysis . . . . . .
145 145 146 147
Appendix A Example Projects . . . . . . . . . . . . . . . . . .
149
A Need for Focus . . . . . . . . . . . . . . . . . . . How Would They Know? . . . . . . . . . . . . . How Proficient Is That? . . . . . . . . . . . . . . Getting the Shaft Back . . . . . . . . . . . . . . . Got It in the Bag! . . . . . . . . . . . . . . . . . . .
149 152 153 154 158
Appendix B Root Cause Analysis Process Guides . . .
161
Generic Process Thinking . . . . . . . . . . . . SIPOC Analysis Form . . . . . . . . . . . . . . . Data Collection and Analysis Tools . . . . . DO IT2 Root Cause Analysis Guide. . . . . DO IT2 Problem-Solving Worksheet . . . . Checklist for Reviewing the Corrective Action Process . . . . . . . . . . . . . . . . . .
161 163 165 166 169
Appendix C Additional Resources . . . . . . . . . . . . . . .
173
Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . Web Sites . . . . . . . . . . . . . . . . . . . . . . . . .
173 174
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
175
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
177
170
List of Figures and Tables
Figure 1.1 Figure 1.2 Figure 1.3 Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Table 3.1 Table 3.2 Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 4.5 Figure 4.6 Figure 4.7 Figure 4.8 Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4
The DO IT 2 problem-solving model . . . . . . . . . . . . Visual depiction of the model . . . . . . . . . . . . . . . . . . Corrective action, root cause analysis, and problem solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . Differentiating between symptoms and causes (physical and system) . . . . . . . . . . . . . . . . . . . . . . . . Levels of causes for machine problem . . . . . . . . . . . Manifestations of multiple causes . . . . . . . . . . . . . . Filters for the corrective action process . . . . . . . . . . Nonconformity risk matrix . . . . . . . . . . . . . . . . . . . . Project decision matrix . . . . . . . . . . . . . . . . . . . . . . . Scrap analysis data for first quarter . . . . . . . . . . . . . Scrap analysis using Paretos . . . . . . . . . . . . . . . . . . . Scrap analysis using pivot tables . . . . . . . . . . . . . . . Effect of Pareto categories . . . . . . . . . . . . . . . . . . . . Using run charts to inform the problem statement . . Setting boundaries for pizza taste problem . . . . . . . Standard process flowchart. . . . . . . . . . . . . . . . . . . . Example flowchart symbols . . . . . . . . . . . . . . . . . . . Deployment flowchart for an engineering change request. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Primary versus administrative/support processes . . . Generic process for policy development and implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SIPOC diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drilling down to find cause . . . . . . . . . . . . . . . . . . . Copier process flow . . . . . . . . . . . . . . . . . . . . . . . . . Logic tree for copier problem . . . . . . . . . . . . . . . . . . Deeper logic tree for copier problem . . . . . . . . . . . . Frequent-flier point error . . . . . . . . . . . . . . . . . . . . .
8 9 10 15 16 20 21 22 25 26 27 28 29 32 38 40 41 41 42 43 44 47 50 52 52 53
Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 6.1 Figure 6.2 Table 6.1 Figure 6.3 Figure 6.4 Table 6.2 Table 6.3 Table 6.4 Figure 7.1 Figure 7.2 Figure 7.3 Figure 7.4 Figure 7.5 Figure 7.6 Table 7.1 Figure 7.7 Figure 7.8 Figure 7.9 Figure 7.10 Figure 7.11 Table 7.2 Table 7.3 Table 7.4 Figure 8.1 Table 8.1 Figure 8.2 Table 8.2 Table 8.3 Table 9.1 Figure 9.1 Figure 10.1
Process-focused logic tree . . . . . . . . . . . . . . . . . . . . Employee voluntary turnover problem . . . . . . . . . . . Losing market share problem . . . . . . . . . . . . . . . . . . Logic tree for lack of training . . . . . . . . . . . . . . . . . . Cause-and-effect diagram . . . . . . . . . . . . . . . . . . . . . Barrier analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Change analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . X and Y (cause and effect) . . . . . . . . . . . . . . . . . . . . Component swap for two identical lines . . . . . . . . . Lab multivari data sheet . . . . . . . . . . . . . . . . . . . . . . Multivari plot for lab . . . . . . . . . . . . . . . . . . . . . . . . Pictogram for injuries . . . . . . . . . . . . . . . . . . . . . . . . Check sheet for hotel room availability problem . . . Data collection sheet for insurance overpays . . . . . . Data collection plan for playground accidents . . . . . Procedure compliance versus results . . . . . . . . . . . . G-chart of number of days between failures . . . . . . Affinity diagram for factors affecting problem-solving effectiveness . . . . . . . . . . . . . . . . . Interrelationship digraph for problem-solving effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pareto of hotel checklist data . . . . . . . . . . . . . . . . . . Drilling down deeper . . . . . . . . . . . . . . . . . . . . . . . . Contingency table: Number of students getting As . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Patterns in run charts . . . . . . . . . . . . . . . . . . . . . . . . Run chart using reordered data . . . . . . . . . . . . . . . . . Histogram analysis . . . . . . . . . . . . . . . . . . . . . . . . . . Scatter diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . Modified scatter diagram . . . . . . . . . . . . . . . . . . . . . Is/Is-not table for packing-line problem . . . . . . . . . . Cause analysis table . . . . . . . . . . . . . . . . . . . . . . . . . Drilling down into problems. . . . . . . . . . . . . . . . . . . Mind map for room-improvement ideas . . . . . . . . . . Use of analogies for gardening tool marketing problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Perceived limits to solution space. . . . . . . . . . . . . . . Decision table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paired comparison . . . . . . . . . . . . . . . . . . . . . . . . . . Action plan tracking form . . . . . . . . . . . . . . . . . . . . Solution-outcome matrix . . . . . . . . . . . . . . . . . . . . . Reasons people resist change . . . . . . . . . . . . . . . . . .
53 54 55 56 58 61 62 66 71 73 73 78 79 80 81 84 85 87 88 88 89 89 90 91 93 94 94 96 97 98 101 102 103 109 110 115 116 122
Figure 10.2 Figure 10.3 Figure 10.4 Figure 10.5 Figure 10.6 Figure 10.7 Figure 11.1 Figure 11.2 Figure 12.1 Figure 12.2 Figure 12.3 Figure A.1 Figure A.2 Figure A.3 Figure A.4 Figure A.5 Figure A.6 Figure A.7 Figure A.8 Figure A.9 Table A.1 Figure A.10 Figure A.11 Figure A.12 Figure B.1 Figure B.2 Table B.1 Table B.2 Figure B.3 Table B.3
Clarifying what we can/can’t affect . . . . . . . . . . . . . Force field analysis . . . . . . . . . . . . . . . . . . . . . . . . . . Changing a complex adaptive system. . . . . . . . . . . . Impact of a punitive culture on root cause analysis . Types of helpers . . . . . . . . . . . . . . . . . . . . . . . . . . . . Facilitator roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Macro causes of human error . . . . . . . . . . . . . . . . . . Flowchart of an incident . . . . . . . . . . . . . . . . . . . . . . Preventive and corrective action . . . . . . . . . . . . . . . . Major components for problem diagnosis . . . . . . . . Thinking as a process . . . . . . . . . . . . . . . . . . . . . . . . Process flowchart for continuous line . . . . . . . . . . . Line downtime by machine . . . . . . . . . . . . . . . . . . . Causes of downtime for Machine B . . . . . . . . . . . . . Logic tree for no audits being conducted . . . . . . . . . PT process flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . PT logic tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pareto of cause for returned parts . . . . . . . . . . . . . . . SIPOC diagram for pinion problem . . . . . . . . . . . . . Pinion manufacturing process . . . . . . . . . . . . . . . . . Runout data collection table . . . . . . . . . . . . . . . . . . . Distributions of runout . . . . . . . . . . . . . . . . . . . . . . . Bagging process flow . . . . . . . . . . . . . . . . . . . . . . . . Bag weights over time . . . . . . . . . . . . . . . . . . . . . . . Generic process thinking . . . . . . . . . . . . . . . . . . . . . SIPOC analysis form . . . . . . . . . . . . . . . . . . . . . . . . Data collection and analysis tools . . . . . . . . . . . . . . DO IT 2 root cause analysis guide . . . . . . . . . . . . . . . DO IT 2 problem-solving worksheet . . . . . . . . . . . . . Checklist for reviewing the corrective action process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
122 123 124 125 127 129 134 141 144 144 145 150 150 151 152 153 154 155 155 156 157 157 159 159 162 164 165 166 169 170
Preface
A
lthough many organizations have invested considerable time and effort to improve their processes, it isn’t unusual to see the same problems popping up over and over. The impacts on customers, end users, employees, profitability, and competitiveness have been well documented in management literature. One factor making such problems highly visible is the formalized management systems guided by documents such as ISO 9001. They require organizations to collect and analyze data on process performance using audits, internal performance indicators, and customer feedback, and problems identified are to have corrective action taken to prevent recurrence. Unfortunately, insufficient effort has been placed on providing guidance on how to carry out an effective diagnosis to identify the causes of problems. Organizations often implement what a participant in one of my courses called a “duct tape solution,” hoping it will address the problem. Meanwhile, the risks associated with repeat problems have significantly increased. Not only is there much greater competition in just about any niche, but organizations and individuals who suffer from failures often expect significant monetary compensation. The increase in transparency brought about by
