Reliability Engineering

4Design for Six Sigma

The concept of Six Sigma originated at Motorola in the 1980s by Dr. Mikel Harry, an engineer. He realized that systems can be improved by measuring and reducing variation. General Electric in the 1990s started implementing these concepts in all their divisions. Impressive quality improvements were experienced. Estimates are that cost savings due to the application of Six Sigma exceeded $300 million within the first 2 years and more than $1 billion by 1999.

Sigma (σ) is a Greek letter used to denote standard deviation, which is used to compare expected outcomes versus failures in a population. Six Sigma is the definition of outcomes as close as possible to perfection. With Six Sigma, the goal is to arrive at 3.4 defects per million opportunities, or 99.9997% perfection. As an example, with Six Sigma, an airline would lose only three to four pieces of luggage for every 1 million pieces that it handles. This is what the Six Sigma process strives to achieve. Over the last 25 years, Six Sigma has been successfully implemented in many industries, from large manufacturers to small businesses, from financial services and the insurance industry to healthcare systems (Barry et al. 2002; Harry and Schroeder 2000; Hoerl 1998; Pande et al. 2000; Pyzdek and Keller 2009).¹

4.1 What Is Six Sigma?

In many organizations, Six Sigma is a business management process that provides tangible business results to the bottom line by continuous process improvement and variation reduction. ...