Six Sigma

Introduction to Six Sigma

In today’s information age, news spreads faster than ever. When an event happens halfway around the world it can become common knowledge within hours or even minutes. Companies must guard their reputation for producing quality products. A single, significant quality incident could result in irreparable damage to brand equity and consumers trust. While there are many quality systems in use today, one methodology has gained tremendous momentum and acceptance throughout industry. The foundational elements of this system can be traced back to the 19th century. In the 1920s, Walter Shewert, a renowned statistician, and sometimes referred to as “the father of statistical quality control”, demonstrated that when process variation reaches three sigmas from the mean or average value, the process requires correction. An engineer working for Motorola named Bill Smith later coined the term Six Sigma. Bill Smith, along with Mikel Harry and Bob Galvin, the then CEO of Motorola, developed a new Quality Management System (QMS) that emphasized the relationship between product performance and the corrections required during manufacture. Their four phase system became the basis on which the current Six Sigma methodology was built. The four phases were Measure, Analyze, Improve and Control.

What is Six Sigma

Six Sigma is a system of statistical tools and techniques focused on eliminating defects and reducing process variability. The Six Sigma process includes measurement, improvement and validation activities. The designation, or title, Six Sigma, relates to the connection between the number of defects per million opportunities and the number of standard deviations found within a process specification. Within statistics, sigma is a reference to the intervals under a normal or “Gaussian” curve. Each interval is equal to one standard deviation or sigma. Therefore, Six Sigma refers to the plus or minus three sigma from the mean of the data under the curve. In the case of a normal distribution, 68.26% of the data points are within plus or minus one sigma from the mean, 95.46% are within two sigma and 99.73% are within three sigma. A process variation exceeding ± 3 sigma should be improved.  With a Six Sigma capable process, only a very small number of possible failures could fall outside specification limits.

Highly skilled personnel trained in the use of the statistical tools and the techniques of Six Sigma implement the Six Sigma methodologies. The Six Sigma training and certification levels are borrowed from the martial arts. The certification or belt levels include white, yellow, green, black and master black belt designations.

Master Black Belt

A Master Black Belt is classically trained in statistical tools, Six Sigma methodology and management processes. Master Black Belts mentor and direct groups of Black Belts and Six Sigma teams through various problems that need to be reviewed. Additionally, Master Black Belts are responsible for the strategy and training of Black Belt level practitioners and below.

Black Belt

A Black Belt receives the highest level of training in the statistical tools of Six Sigma. Black Belts, as a rule, develop the plans for Six Sigma project implementation. Their responsibilities include creating project plans, leading cross-functional projects and directing team members, including Green and Yellow Belts.  Black Belts usually train other team members on the proper use of Six Sigma tools and techniques, such as control charts, histograms and Root Cause Analysis (RCA).

Green Belt

Green Belts report to a Black Belt and lead process improvement teams part time. Approximately 25- 50% of their time should be devoted to working on Six Sigma projects, usually within their own functional areas.  Green Belts receive training on DMAIC methodology, statistical tools, proper data collection and analysis of the data collected.

Yellow Belt

A Yellow Belt should have a basic understanding of Six Sigma, statistical tools and DMAIC methodology. Yellow Belts are often members of the workforce recognized for their skill, knowledge and experience with the process in question. They often fulfill the role of Subject Matter Expert (SME) for the process. They are valuable during the measure phase of a project, gathering data, measurements and metrics.  However, Yellow Belts are not typically involved in the data analysis process.

Six Sigma is more than a quality system, a set of statistical tools, a certification system or a method for process improvement. Some perceive it as a philosophy that embraces the belief that all business processes are measurable and can be improved.


Why Implement Six Sigma

With rising material cost and ever-increasing competition, organizations must seek out methods to increase efficiency. By implementing Six Sigma methodology, an organization can improve efficiency through identification and resolution of product or part defects and minimize the variation within a process. Each Six Sigma project follows a defined sequence of steps and includes specific improvement targets. Some examples could include:

  • Reduction in process cycle time
  • Reduction of scrap generated by a process
  • Increasing customer satisfaction
  • Reduction in the number of factory defects
  • Reduction or elimination of costly reworks

Every one of the examples listed would have a positive effect on the bottom line of any organization. Six Sigma is not limited to the manufacturing industry. The tools and techniques are currently being used to improve processes in all type of businesses and organizations. The tools can improve manufacturing processes, office or business processes and customer service processes.

How to Implement Six Sigma

A typical Six Sigma project measures the current state and increases the performance of the business process to a new and statistically significant improved state using statistical tools. Standard Six Sigma capability refers to a very small number of possible failures that can exist outside the specification.

The method most frequently associated with Six Sigma is DMAIC, which stands for Define, Measure, Analyze, Improve and Control. Before beginning any Six Sigma improvement project, it is necessary to select a process that, if improved, would result in reduced cost, superior quality or increased efficiency. The process also must possess measurable data because what you cannot measure you cannot improve. The process selected may currently be experiencing quality problems or generating a large amount of scrap.