1.3 Statistics and Six Sigma
Many Six Sigma tools and methods involve statistics. What exactly is meant by statistics, and why is statistics such an integral part of Six Sigma management? To understand the importance of statistics for improving quality, you can go back to a famous 1925 quote of Walter Shewhart, widely considered to be the father of quality control:
The long-range contribution of statistics depends not so much upon getting a lot of highly trained statisticians into industry as it does in creating a statistically minded generation of physicists, chemists, engineers, and others who will in any way have a hand in developing and directing the production processes of tomorrow.
This quote is just as valid today as it was more than 75 years ago. The goal of this book is not to make you a statistician. The goal is to enable you to learn enough so that you will be able to use the statistical methods that are involved in each phase of the DMAIC model. Using Minitab and/or JMP statistical software will help you achieve this goal while at the same time minimize your need for formulas and computations.
Table 1.1 summarizes the statistical methods that are commonly used in the various phases of the DMAIC model.
Table 1.1 Phases of the DMAIC Model, Statistical Methods Used, and Chapters in This Book
Phase of DMAIC Model |
Statistical Methods |
Chapters |
Define |
Tables and Charts |
3 |
|
Descriptive Statistics |
4 |
|
Statistical Process Control Charts |
11 |
Measure |
Tables and Charts |
3 |
|
Descriptive Statistics |
4 |
|
Normal Distribution |
5 |
|
Analysis of Variance |
6, 7, 8 |
|
Statistical Process Control Charts |
11 |
Analyze |
Tables and Charts |
3 |
|
Descriptive Statistics |
4 |
|
Analysis of Variance |
6, 7, 8 |
|
Regression Analysis |
9, 10 |
|
Statistical Process Control Charts |
11 |
Improve |
Tables and Charts |
3 |
|
Descriptive Statistics |
4 |
|
Analysis of Variance |
6, 7, 8 |
|
Regression Analysis |
9, 10 |
|
Design of Experiments |
8 |
Control |
Statistical Process Control Charts |
11 |