Six Sigma and beyond: Deming and Six Sigma

"Six Sigma and Beyond" is the first in a Quality eLine series by David Schwinn, an independent consultant in Jackson, MI with experience in automotive-related industries and community quality training. This month's comments focus on Six Sigma, the new management strategy promoted by the American Society for Quality (ASQ), General Electric, Motorola, and others. It introduces basics of six sigma as a management tool, comparing its approach to that of W. Edwards Deming. Future columns will respond to user questions, challenges, and comments. Address these to Schwinn via PQ Systems, at support@pqsystems.com.

February's Quality eLine feature, Six Sigma Quality and Six Sigma Capability: The Inside Story," pointed out that six sigma can be summarized as a defect level of 3.4 defects per million. Most organizations currently operate at a level of 2,700 defects per million. That's quite a gap! In Six Sigma, Mike Harry and Richard Schroeder (New York: Doubleday, 2000) suggest that the cost of defects for most companies is about 20-30% of revenue, compared to 1% for Six Sigma companies. The reasons for an emerging interest in reducing defects are clear, and Six Sigma offers a way to address the issue of quality improvement.

Looking at the history of quality improvement and statistical process control (SPC) helps to understand the emergence of the Six Sigma approach on the heels of earlier approaches of W. Edwards Deming and others.

With the development of SPC in earlier decades of the 20th century and a recognition of its importance in quality improvement, organizations embraced the management philosophy of W. Edwards Deming, who had helped the Japanese economy get back on its feet after World War II. The lesson of quality management was clear, translating into reduction of waste and improvement of products and services.

By the early eighties, it had become apparent that embracing SPC and the philosophy of continual improvement was imperative for companies expecting to compete with Japanese industry. Deming's approach took companies a long way toward improved cost and productivity in a global economy.

There are both differences and similarities between Deming's ideas and the Six Sigma approach. The logic of the Six Sigma approach, for example, is that reducing defects will reduce costs and improve profits--a concept that is not radically different from Deming's "Chain Reaction." It is in the interest of any organization to understand the connection between waste or defects and profits. Deming considered the sales advantage of superior quality to be equally important as a profit driver. A company's reputation can be tied to its attention to quality, manifesting itself throughout an organization and the processes it undertakes.

The Six Sigma process can be seen to offer a parallel to Deming's Plan-Do-Study-Act Cycle, although Six Sigma brings experimental design and regression analysis to the forefront in the "plan" phase. Six Sigma also emphasizes design as a key function for achieving six sigma performance levels, and devotes attention to planning the design phase of production. Deming, too, emphasized "Plan" in his four-state cycle, promoting the importance of establishing a relationship between desired output and required input as well as necessary production processes.

Perhaps the most striking difference between the approaches is Deming's focus on the responsibilities of management, outlined in his "The 14 Obligations of Management," and "The Deadly Diseases." The Six Sigma approach, by contrast, lays out a more rigid structure of roles and responsibilities throughout an organization, including executive management, a senior champion, deployment champions, project champions, deployment master black belts, project master black belts, project black belts, process owners, and six sigma green belts. This structure, it is said, is central to the Six Sigma model for success.

That's a quick overview of Six Sigma, as a way of offering a comparison with the Deming approach to quality improvement. Please send your questions and comments, or suggestions for future topics related to Six Sigma, to support@pqsystems.com