In this lesson, you’re expected to learn about:
– the basics of the six sigma metric
– the meaning of different sigma levels
– tool and techniques used in different models
What is Six Sigma?
Six-Sigma is a statistical concept to describe accuracy and quality levels in a process, product, or service, which can lead to a competitive advantage in the marketplace.
The word sigma is associated with a statistical term, standard deviation, which is the distance from the mean (average).
Six-Sigma is a strategy, discipline, system, program, and tool to achieve quality improvement continuously, to solve problems, to improve functions and features of a product or service, to reduce cost and time, and to increase customer satisfaction.
Meaning of Different Sigma Levels
• Three-Sigma means 66,800 defects in a million parts produced.
• Four-Sigma means 6,210 defects in a million parts produced.
• Five-Sigma means 230 defects in a million parts produced.
• Six-Sigma means 3.4 defects in a million parts produced.
The goal of reaching Six-Sigma from Three-Sigma is a challenging one as it is a non-linear process to reach the goal.
Six-Sigma follows an improvement model called DMAIC, which stands for define, measure, analyze, improve, and control stage.
D defines the project’s purpose, scope, and outputs, M measures the process and collects data, A analyzes the data to ensure
repeatability and reproducibility, I improves or redesigns the existing process, and C controls the new or modified process for increased performance.
Six-Sigma redefines quality performance as defects per million opportunities (dpmo) and is calculated as:
dpmo = (Defects per Unit) x 1,000,000 / Opportunities for Error
Examples of tools and techniques used in the Define stage include brainstorming, cause-and-effect diagram, and process mapping.
Examples of tools and techniques used in the Measure stage include cause-and-effect diagram and process mapping.
Examples of tools and techniques used in the Analyze stage include regression and correlation analysis and process mapping.
Examples of tools and techniques used in the Improve stage include brainstorming, simulation, design of experiments, and process mapping.
Examples of tools and techniques used in the Control stage include mistake-proofing (Poka-yoke), statistical process control, and control charts.
Design for Six-Sigma (DFSS) is a proactive approach in preventing problems from occurring in the first place and/or in resolving problems after they occur. The focus is on functional and quality improvement at the early design stage.
An approach to DFSS is established in terms of DCOV model, which stands for define, characterize, optimize, and verify.
Examples of tools and techniques used in the Characterize stage include design of experiments and TRIZ (a problem-solving tool).
Examples of tools and techniques used in the Optimize stage include design of experiments, simulation, mistake-proofing, and control charts.
Examples of tools and techniques used in the Verify stage include design walkthroughs and reviews and product tests.
All of these players assume defined roles and responsibilities and need specific training with varying lengths to make the Six-Sigma program a success.
Green Belts are salaried employees who have a dual responsibility in implementing Six-Sigma in their function and carrying out their regular duties in that function. They gather and analyze data in support of a Black Belt project and receive a simplified version of Black Belt training.
Yellow Belts are seasoned salaried employees who are familiar with quality improvement processes.
Master Black Belts are also salaried employees who have a full-time responsibility in implementing Six-Sigma projects. They require soft skills, need some knowledge in statistics, and need more knowledge in problem-solving and decision-making tools and techniques, as they train Black Belts and Green Belts.
Senior Champions develop plans, set priorities, allocate resources, and organize projects. Project Champions deploy plans, manage projects that cut across the business functions, and provide managerial and technical guidance to Master Black Belts and Black Belts.