Page 43 - Design for Six Sigma a Roadmap for Product Development

Chapter
2

Six Sigma and Lean
Fundamentals

2.1 What Is Six Sigma?
Six Sigma is a methodology that provides businesses with the tools to
improve the capability of their business processes. For Six Sigma, a
process is the basic unit for improvement. A process could be a product
or a service process that a company provides to outside customers, or it
could be an internal process within the company, such as a billing or
production process. In Six Sigma, the purpose of process improvement
is to increase performance and decrease performance variation. This
increase in performance and decrease in performance variation will
lead to defect reduction and improvement in profits, to employee morale,
and quality of product, and eventually to business excellence.
Six Sigma is an extremely successful business management system
in industry today. It has been credited with saving billions of dollars
for companies since the early 1990s. Developed by Motorola in the mid-
1980s, the methodology became well known only after Jack Welch from
GE made it a central focus of his business strategy in 1995.
The name “Six Sigma” derives from statistical terminology; Sigma
( ) means standard deviation. For normal distribution, the probability
of falling within a 6 sigma range around the mean is 0.9999966. In a
production process, the “Six Sigma standard” means that the defectiv-
ity rate of the process will be 3.4 defects per million units. Clearly Six
Sigma indicates a degree of extremely high consistency and extremely
low variability. In statistical terms, the purpose of Six Sigma is to
reduce variation to achieve very small standard deviations.
Compared with other quality initiatives, the key difference of Six
Sigma is that it applies not only to product quality but also to all

21
Copyright © 2009, 2003 by The McGraw-Hill Companies, Inc. Click here for terms of use.