Lean Six Sigma Using Sigmaxl and Minitab ABOUT the AUTHORS
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Lean Six Sigma Using SigmaXL and Minitab ABOUT THE AUTHORS ISSA BASS is a Master Black Belt and senior consultant with Manor House and Associates. He is the founding editor of SixSigmaFirst.com. Bass has extensive experience in qual- ity and operations management, and is the author of Six Sigma Statistics with Minitab and Excel. BARBARA LAWTON, Ph.D., is a Six Sigma Black Belt and has been improving manufacturing processes using Lean tech- niques and Six Sigma for more than 15 years, in various industries on three continents. Dr. Lawton specializes in data analysis, and is a keen experimentalist and problem solver, using a wide range of statistical tools. She currently works for one of the world’s leading aerospace organizations in the UK. Lean Six Sigma Using SigmaXL and Minitab Issa Bass Barbara Lawton, Ph.D. New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Copyright © 2009 by The McGraw-Hill Companies, Inc. 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To my mother Dema Diallo and my pretty niece Sira Basse —Issa Bass To my brother Peter and my late parents, Barbara and Derek. To Professor Ron Pethig, Russel Johnson and Dr. Harry Watts for support and driving me toward a successful career. To Issa Bass who has sent me on a new journey. Finally, to Derek Richards, who taught me the mathematical foundation that has led to a successful engineering career. Thank you. —Dr. Barbara Lawton This page intentionally left blank Contents Preface xiii Acknowledgments xv Introduction 1 An Overview of SigmaXL 3 SigmaXL menu bar 3 SigmaXL templates 5 Solution 6 Chapter 1. Defi ne 9 Project Planning 9 The Gantt chart 10 Program evaluation and review technique (PERT) 13 Project Charter 15 Project number 16 Project champion 16 Project defi nition 16 Project description 17 Value statement 17 Stakeholders 17 Project monitoring 17 Scheduling 17 Alternative plans 17 Risk analysis 17 Capturing the Voice of the Customer 17 Capturing the voice of the external customer 19 Capturing the voice of the internal customer 21 Capturing the voice of the customers of a project 21 Capturing the voice of the next step in the process 21 Critical-to-Quality Tree 22 Kano analysis 24 Suppliers-Input-Process-Output-Customers (SIPOC) 26 vii viii Contents Cost of Quality 29 Assessing the cost of quality 29 Cost of conformance 30 Preventive cost 30 Appraisal cost 31 Cost of nonconformance 31 Internal failure 31 External failure 31 Optimal Cost of Quality 34 Cost of Quality According to Taguchi 36 Stakeholder Analysis 38 Force fi eld analysis (FFA) 39 Chapter 2. Measure 43 Data Gathering 43 Data Types 43 Attribute data 44 Variable data 44 Locational data 44 Basic Probability 44 So what is probability? 44 Discrete versus continuous distributions 44 Expected value, variance, and standard deviation of discrete distribution 45 Discrete probability distributions 47 Approximating binomial problems by Poisson distribution 56 Continuous distribution 56 Z transformation 58 Planning for Sampling 66 Random Sampling versus Nonrandom Sampling 67 Random sampling 67 Nonrandom sampling 68 Nonsampling errors 68 Sampling error 68 Central Limit Theorem 69 Sampling distribution of the mean X 70 Estimating the population mean with large sample sizes 71 Estimating the population mean with small sample sizes and r unknown t-distribution 74 b 2 Distribution 77 Estimating sample sizes 80 Sample size when estimating the mean 81 Measurement Systems Analysis 82 Precision and Accuracy 86 Measurement errors due to precision 86 Variations due to accuracy 93 Gauge bias 94 Gauge linearity 96 Contents ix Attribute Gauge Study 100 Assessing a Processes Ability to Meet Customers’ Expectations—Process Capability Analysis 103 Process Capabilities with Normal Data 106 Estimating Sigma 106 Short-term sigma 106 Long-term sigma 107 Potential Capabilities 107 Short-term potential capabilities, Cp and Cr 107 Long-term potential performance 109 Actual capabilities 109 Capability indices and parts per million 111 Process capability and Z transformation 111 Minitab output 115 Taguchi’s capability indices CPM and PPM 116 Process Capability Analysis with Nonnormal Data 121 Normality Assumption and Box-Cox Transformation 122 Process Capability Using Box-Cox Transformation 123 Process Capability Using Nonnormal Distribution 128 Lean Six Sigma Metrics 130 Six Sigma metrics 131 First time yield (FTY) 133 Lean metrics 134 Work in Progress (WIP) 141 Chapter 3. Analyze 143 Brainstorming 143 Nominal Group Process 143 Affi nity Diagram 144 Cause-and-Effect Analysis 146 Pareto Analysis 149 Using Minitab 152 Fault Tree Analysis 152 Seven Types of Waste 154 Overproduction 156 Wait 157 Unnecessary inventory 158 Motion 158 Unnecessary transportation 158 Inappropriate processing 159 Product defects 159 Lean Approach to Waste Reduction 159 Cycle Time Reduction 161 Takt time 162 Batch versus one-piece fl ow 164 Data Gathering and Process Improvement 165 Value stream mapping 166 How to map your value stream 167 x Contents Failure Mode and Effect Analysis 168 Failure mode assessment 170 Action plan 171 Hypothesis testing 174 P-value method 177 Nonparametric Hypothesis Testing 182 Chi-square test 182 Contingency analysis—Chi square test of independence 185 The Mann-Whitney U test 187 Normality testing 195 Normalizing data 196 Analysis of Variance 198 Mean square 200 Regression Analysis 204 Simple linear regression (or fi rst-order linear model) 206 Multiple regression analysis 210 Chapter 4. Improve 213 Design of Experiments 213 Factorial Experiments 215 Main effect and interaction effect 216 2k Factorial design 217 22 Two factors and two levels 218 Degrees of freedom 222 Using Minitab 222 Interpretation 225 Using SigmaXL 225 Regression Model 234 SigmaXL output 236 Residual analysis 236 2k Two levels with more than 2 factors 237 Main effects for 23—two levels with three factors 239 Blocking 252 Confounding 254 - 2k 1 Fractional factorial design 256 - 23 1 Fractional factorial design 258 - 24 1 Factorial design 260 Design resolution 260 The Theory of Constraints 268 The process throughput is tied to the bottleneck 271 TOC Metrics 273 Thinking Process 273 The Goldratt Cloud 274 The Goldratt Reality Trees 275 Current reality tree 276 Future reality tree 278 5s 280 Contents xi Chapter 5.