vii
Contents
Preface ......................................................................................................................xi
Acknowledgments .............................................................................................. xiii
About the Authors ................................................................................................xv
Section I Background
1. Introduction to Six Sigma Quality ..............................................................3
1.1 Denitions ..............................................................................................3
1.1.1 Defects Per Million Opportunities (DPMO) ........................5
1.1.1.1 DPMO Example 1 .....................................................5
1.1.1.2 DPMO Example 2 .....................................................7
1.1.1.3 DPMO Example 3 .....................................................9
1.2 DMAIC Approach ............................................................................... 10
1.3 Book Outline ........................................................................................ 11
References .......................................................................................................13
2. Quality Analysis and Improvement Tools/Techniques Used
in This Book ..................................................................................................15
2.1 Condence Interval Estimation ........................................................15
2.2 Hypothesis Testing .............................................................................15
2.3 Chi-Square Analysis ........................................................................... 16
2.4 Process Capability Analysis .............................................................. 16
2.5 Binary Logistic Regression ................................................................ 17
2.6 Item Analysis ....................................................................................... 17
2.7 Cluster Analysis ..................................................................................17
2.8 Mixture Design and Analysis of Experiments ............................... 17
2.9 Multivariate Analysis ......................................................................... 18
2.10 Pareto Chart ......................................................................................... 18
2.11 Cause-and-Effect Diagram ................................................................ 18
2.12 Gage Repeatability and Reproducibility Analysis ......................... 18
2.13 Taguchi Design and Analysis of Experiments ...............................19
2.14 Factorial Design and Analysis of Experiments .............................. 19
2.15 Statistical Control Charts ................................................................... 19
2.16 Normality Test .....................................................................................19
2.17 Analysis of Variance (ANOVA) .........................................................20
References .......................................................................................................20
viii Contents
Section II Six Sigma Case Studies
3. Condence Intervals to Assess Variation in Fat Content
at a Fast-Food Restaurant ............................................................................23
3.1 Dene Phase ........................................................................................23
3.2 Measure Phase .....................................................................................23
3.3 Analyze Phase ..................................................................................... 31
3.4 Improve Phase ..................................................................................... 31
3.5 Control Phase .......................................................................................42
4. Hypothesis Testing for Quality Control at a Manufacturing
Company .........................................................................................................43
4.1 Dene Phase ........................................................................................43
4.2 Measure and Analyze Phases ...........................................................44
4.2.1 Test 1 ........................................................................................44
4.2.2 Test 2 ........................................................................................46
4.2.3 Test 3 ........................................................................................47
4.3 Improve and Control Phases .............................................................60
5. Chi-Square Analysis to Verify Quality of Candy Packets .................. 61
5.1 Dene Phase ........................................................................................ 61
5.2 Measure Phase ..................................................................................... 61
5.3 Analyze Phase .....................................................................................62
5.4 Improve and Control Phases ............................................................. 79
6. Process Capability Analysis at a Manufacturing Company ................81
6.1 Dene Phase ........................................................................................82
6.2 Measure Phase .....................................................................................82
6.3 Analyze Phase .....................................................................................84
6.4 Improve Phase .....................................................................................88
6.5 Control Phase ..................................................................................... 103
7. Binary Logistic Regression to Predict Customer Satisfaction
at a Restaurant ............................................................................................. 105
7.1 Dene Phase ...................................................................................... 105
7.2 Measure Phase ................................................................................... 106
7.3 Analyze Phase ................................................................................... 106
7.4 Improve and Control Phases ........................................................... 118
ixContents
8. Item Analysis and Cluster Analysis to Gather “Voice of the
Customer” (VOC) Data from Employees at a Service Firm ............... 119
8.1 Dene Phase ...................................................................................... 119
8.2 Measure Phase ...................................................................................120
8.3 Analyze Phase ................................................................................... 124
8.4 Improve and Control Phases ........................................................... 135
9. Mixture Designs to Optimize Pollution Level and Temperature
of Fuels .......................................................................................................... 137
9.1 Dene Phase ...................................................................................... 137
9.2 Measure Phase ................................................................................... 137
9.3 Analyze Phase ................................................................................... 137
9.4 Design and Verify Phases ................................................................ 160
10. Multivariate Analysis to Reduce Patient Waiting Time
at a Medical Center ..................................................................................... 161
10.1 Dene Phase ...................................................................................... 161
10.2 Measure Phase ................................................................................... 161
10.3 Analyze Phase ................................................................................... 163
10.4 Improve Phase ................................................................................... 183
10.5 Control Phase .....................................................................................183
11. Pareto Chart and Fishbone Diagram to Minimize Recyclable
Waste Disposal in a Town ......................................................................... 185
11.1 Dene and Measure Phases ............................................................ 185
11.2 Analyze Phase ................................................................................... 187
11.3 Improve and Control Phases ........................................................... 194
12. Measurement System Analysis at a Medical
Equipment Manufacturer .........................................................................195
12.1 Dene Phase ...................................................................................... 195
12.2 Measure Phase ................................................................................... 195
12.3 Analyze, Improve, and Control Phases ......................................... 213
13. Taguchi Design to Improve Customer Satisfaction of an Airline
Company ....................................................................................................... 215
13.1 Dene Phase ...................................................................................... 215
13.2 Measure Phase ................................................................................... 218
13.3 Analyze Phase ................................................................................... 219
13.4 Improve and Control Phases ........................................................... 229
x Contents
14. Factorial Design of Experiments to Optimize a Chemical
Process ...................................................................................................... 231
14.1 Dene Phase ...................................................................................... 231
14.2 Measure Phase ................................................................................... 231
14.3 Analyze Phase ...................................................................................237
14.4 Improve and Control Phases ........................................................... 255
15. Chi-Square Test to Verify Source Association with Parts
Purchased and Products Produced .........................................................257
15.1 Dene Phase ......................................................................................257
15.2 Measure Phase ...................................................................................257
15.3 Analyze Phase ...................................................................................258
15.4 Improve and Control Phases ........................................................... 272
Appendix .............................................................................................................273

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