Six Sigma is the current call to quality. Some individuals see it as a new system for companies to adopt and make into a permanent part of their corporate culture. Others see Six Sigma as the current definition for the quality improvement process.

Articles abound on the large savings companies achieve as a result of implementing Six Sigma. Companies such as Johnson & Johnson reported savings of $200 million in 1999, $350 million in 2000 and $500 million in 2001 (Bertels, 2003). Other companies reported similar results. These companies had one thing in common; they adopted and implemented a strong continuous improvement process in the 1980s and early 1990s. Six Sigma allowed these companies to achieve new heights in the quality movement.

On the other hand, the author has seen only one reference that states that pure Six Sigma achieves these results only when implemented in high performance companies (Quality Council of Indiana, 2001). Companies that are low or medium performing should concentrate on the basics of process control and continuous improvement. These basics include implementing the concept of Statistical Thinking. Statistical Thinking focuses on three premises:

1. All work is done in a process –
   Companies must develop a detailed understanding of their critical processes.
2. All processes show variation –
   Companies need to develop measurement systems that monitor process and product variation.
3. The key to success is the reduction in variation –
   Companies must develop a continuous improvement program that identifies and reduces the causes of variation.

Six Sigma evolved because each tool of quality improvement takes a company only so far. However, if a company is going to effectively use the new tools, they must master the basic tools. One tool that has been added to the Six Sigma tool box is Design of Experiments (DOE). DOE must be used with care because it has some underlying statistical assumptions which include identically and independently distributed data. In SPC terms, this is achieved by having stable processes. Thus, the first steps in traditional continual improvement and the first steps in Six Sigma are identical; remove the special causes of variation. Six Sigma methodologies include training in a number of management tools such as project management, financial management and change management.

Six Sigma has a management structure that uniquely integrates into a traditional business structure. Executives must commit to the Six Sigma. Part of this commitment includes serving as champions for Six Sigma projects. This role has a three-fold effect:

1. Projects are selected that have a direct impact on profitability, productivity or quality.
2. Executives have a vested interest in seeing successful completion of projects.
3. A reporting system is developed that minimizes the filtering of critical information through levels of management.

These projects are typically high impact and short term in nature. Projects are to be successfully completed in four months. In order for this to work, a Six Sigma company needs to have a track record of using the basic tools of continuous improvement to successfully improve processes.

Companies commit resources to development of a group of highly trained specialists (Black Belts) in the quality improvement process. These are individuals that report directly to the corporate office, while being located at the plant level to lead continuous improvement projects. It is the sole function of the Black Belts to manage and lead quality improvement projects. The Six Sigma literature recommends that there should be one Black Belt for every 100 employees.

The Black Belts are supported by Green Belts. The Green Belts are individuals trained in Six Sigma methodology and work on Six Sigma projects in addition to other assigned work responsibilities. Typically, a Green Belt spends about 25 to 50 percent of their time working on Six Sigma Projects.

Continuous Improvement is achieved through teams using a systematic continuous improvement process. However, the PDCA (Plan, Do, Check, Act) cycle has been improved to DMAIC (Define, Measure, Analyze, Improve Control). Some additional acronyms include:

• DPMO (Defects per Million Opportunities) –
  A measure of six sigma effectiveness.
• SIPOC (Suppliers, Input, Process, Output, Customers) –
  A means to properly define the components of any processes.
• DFSS (Design for Six Sigma) –
  Designing quality into processes and products.
• DMADV (Define, Measure, Analyze, Design, Verify) –
  The process used for DFSS.

Six Sigma can be a powerful tool to maintain the quality improvement process. It is not an easy process to implement. To achieve the gains that are reported in the literature, the company must have an existing active process control and continuous improvement process.

Reference:

Quality Council of Indiana, "Certified Six Sigma Black Belt Primer." Quality Council of Indiana, Terra Haute, IN, 2001.

Bertels, T., "Rath and Strong’s Six Sigma Leadership Handbook," John Wiley and Sons, New York, 2003.

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