Six Sigma Tools Know-it-all: Six Sigma Definition

Six Sigma is an approach to quality-control and business process improvement that was developed by Motorola in the mid-80s which strives to virtually remove imperfections and flaws altogether. Its main focus was to reduce manufacturing defects to miniscule proportions through constant evaluation and improvement. Since then, Six Sigma has evolved into a philosophy that deals with business processes of all sorts, not just tied to physical production. In most modern applications, Six Sigma is an approach that strives for near perfection through the power of data-driven analysis and continual improvement.

The name for Six Sigma comes from the basic statistical principle that underpins the approach – the nearest specification limit should be six standard statistical deviations away from the mean in any business process. To achieve this, a defect of any sorts should not appear more often than 3.4 times per 1 million opportunities. Being heavily rooted in statistics, Six Sigma implies constant measurement and analysis of the performance of each process. To put it simply, this methodology puts forward goals that are quite ambitious, but that are measurable and that are subject to detailed analysis.

Of course, Six Sigma wouldn’t be a complete methodology without including the means to make improvements, let alone a methodology with such popularity and acclaim. In order to help businesses reach their lofty goals, it relies on two essential sets of methods – DMAIC and DMADV.


DMAIC is an abbreviation that stands for Define, Measure, Analyze, Improve, and Control which are its five phases. This is the approach used when working to improve an existing business process that is performing below the Six Sigma standards. The Define phase is used to set the project’s goals mainly from the point of view of the customer while the Measure phase is concerned with gathering the relevant data. The Analyze phase deals with finding cause-and-effect relations between different factors in an attempt to find the root causes of any underperformance. The Improve phase deals with optimizing the process using multiple data-driven techniques in order to develop a process that would meet the Six Sigma standards while the Control phase looks to implement and sustain them with additional measures until the quality reaches the desired levels.


While the DMAIC focuses on existing processes, the DMADV (Define, Measure, Analyze, Design, and Verify) is the methodology that deals with designing new processes specifically to work with the Six Sigma framework and to produce results that would fit the Six Sigma quality standards. This is why it’s sometimes referred to as DFSS which stands for Design for Six Sigma. Instead of dealing with an existing process and the data than can be gathered about it, this sub-methodology uses any available data to create an inform initial design that can be tested and verified in practice in the last phase where after a successful pilot, the process usually becomes subject to the DMAIC methodology and main it’s Control phase.

Another important aspect of Six Sigma is the roles it defines for the professionals that are in charge of its implementation. They are mastery of the methodology is signified by belt colors ranging from dark to light much like the belts in martial arts.
Master Black Belt – Develops strategies and metrics, coaches lower level belts
Black Belt – Leads Black Belt projects that require the highest level of expertise and giving solutions to challenging problems
Green Belt – Assists Black Belts and/or lead Green Belt projects
Yellow Belt – Participates in projects and takes part in process improvement
White Belt – Understands the basics of the methodology but cannot be part of project teams yet

While the belt roles are concerned with professionally operating Six Sigma projects and are subject to official Six Sigma certification, projects need to interface with the company and its values, goals and management. That’s why Six Sigma also defines Champions and Executives as roles that guide and support the whole Six Sigma program and its projects.

Learn more about Six Sigma and the tools of the profession by going to www.6sigma.us. Learn more about our training and certifications that will allow you to use the Fishbone Diagram tool effectively.

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