Six Sigma

Six Sigma is an approach to data-driven management that seeks to improve quality by measuring how many defects there are in a process and systematically eliminating them until there are as close to zero defects as possible. In 1984, a Motorola engineer named Bill Smith developed the Six Sigma management system to reduce the variations in Motorola’s electronic manufacturing processes that were causing product defects. Since then, the strategies, tools and cultural norms that support the management system have been adopted by companies in a wide variety of industries and the meaning of the word “defect” has broadened to include any deficiency that prevents a company from meeting its customer’s needs. 

In statistics, the Greek letter sigma is used to denote standard deviation from the mean. In the 1920s, statistical quality control pioneer Walter Shewhart proposed that in manufacturing, three sigma from the mean is the tipping point that indicates a process has too many defects and requires correction. This was the accepted norm for many years, until Bill Smith proposed gathering and analyzing data at a more granular level and making six sigma the point at which a process has to be corrected. Because it is almost impossible to achieve zero defects, a concept known as infinity sigma, six sigma allows for 3.4 defects per million opportunities for a defect to occur. In contrast, three sigma allows for 66,807 defects per million opportunities. 

Once the necessary data has been gathered, a company that is managed with Six Sigma methodologies uses statistics to create a baseline sigma. The baseline illustrates how close – or how far – the company is from achieving six sigma and serves as a measuring stick for assessing future improvement.  Six Sigma proponents claim its benefits include up to 50% process cost reduction, cycle-time improvement, less waste of materials, a better understanding of customer requirements, increased customer satisfaction, and more reliable products and services. Motorola hold the federal trademark for Six Sigma and it is generally acknowledged that Six Sigma can be costly to implement and can take several years before a company begins to see bottom-line results. In 1995, General Electric Chief Executive Officer (CEO) Jack Welch’s very public endorsement of Six Sigma helped businesses outside of manufacturing understand how Six Sigma methodologies can be used to improve customer satisfaction in any industry. 

There are two very important methodologies for executing a Six Sigma initiative: Six Sigma DMAIC and Six Sigma DMADV. Each term’s name is derived from the major steps in its process, but each has its own use. DMAIC (define, measure, analyze, improve, control) is used to correct a process that already exists. DMADV (define, measure, analyze, design, validate) is used to create a new process. 

Six Sigma DMAIC

Here is a step-by-step breakdown of Six Sigma DMAIC:

  1. Define: Identify the project goals and all customer deliverables.
  2. Measure: Understand current performance.
  3. Analyze: Determine root causes of any defects.
  4. Improve: Establish ways to eliminate defects and correct the process.
  5. Control: Manage future process performance.
DMAIC: Define, measure, analyze, improve, control

Six Sigma DMADV

Here is a step-by-step breakdown of Sigma DMADV. The first three steps of this methodology are identical to DMAIC. Because the two acronyms are so similar, some companies use the acronym DFSS (Design For Six Sigma) in place of DMADV. 

  1. Define: Identify the project goals and all customer deliverables.
  2. Measure: Understand current performance.
  3. Analyze: Determine root causes of any defects.
  4. Design: Create a process that meets customer needs and expectations.
  5. Verify: Ensure process designed meets customer needs and performs adequately.
DMADV: Design, measure, analyze, design, verify

When contemplating Six Sigma DMAIC versus DMADV, it is important to understand the circumstances in which each should be used. The DMAIC methodology should be used when an existing product or service is not meeting customer needs or performing to its highest standards. The DMADV methodology should be used when an organization is developing a new product or service, or when using DMAIC for a current project or process fails.

Six Sigma and Lean Six Sigma certification and training

All Six Sigma processes are executed by Six Sigma White Belts, Six Sigma Yellow Belts, Six Sigma Green Belts or Six Sigma Black Belts, which are then overseen by a Six Sigma Master Black Belt -- terms created by Motorola. The International Association for Six Sigma Certification (IASSC) is one organization that issues certifications. At IASSC, yellow, green and black belt exams are designed to measure a person's knowledge of topics contained within IASSC's Universally Accepted Lean Six Sigma Body of Knowledge. Another training organization offering belts from white to black is 6

six sigma, belt levels, certification

Many training organizations also offer Lean Six Sigma training. Like Six Sigma, Lean processes are used by businesses to streamline manufacturing and production processes. The differentiator is that Lean cuts out unnecessary and wasteful steps in the creation of products or service.

This was last updated in April 2017

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