Six Sigma Glossary from MiC Quality


Six Sigma Terms
Black Belt

The Black Belt is the team leader responsible for the operation and outcomes of major Six Sigma projects. To achieve Black Belt status it is necessary to demonstrate mastery of the tools, through an examination and completing a project in industry.

Big Y

The important high level business result that the Six Sigma project seeks to improve. The 'Big Y' should be linked to the critical customer requirements.

The Big Y is often used to generate 'little y' operational objectives that must be improved to achieve Big Y improvements. The Big Y might be to reduce lead times, the Little y could be the inventory performance at the warehouse.


Senior managers who champion the project, ensure that they are properly resourced and obtain support in the organization.

Change Agent

A person who leads change within an organization, by championing the change, and managing and planning its implementation. The role can be official or voluntary.


See Cost of Poor Quality

Cost of Poor Quality

The costs of poor quality including internal failure costs, external failure costs, appraisal costs and prevention costs.

Critical to Quality

The key measurable characteristics of a product or process that are critical to meeting the customer expectations.


See Critical to Quality

Design for Six Sigma

A version of the Six Sigma approach that is used during the design of a product, service or process.


See Design for Six Sigma


The five main steps in a Six Sigma Program stands for Define, Measure, Analyze, Improve, Control. A Six Sigma project works through each of these steps:


  • the customer and their 'Critical To Quality' issues and expectations
  • the business processes that are involved, the boundaries of the project
  • create a process map
  • decide on the metrics 'Big Y', little y's and the x's
  • form a project team and develop a project charter


  • the existing process by gathering data from the process


  • the data
  • identify the gaps between existing and desired performance
  • identify sources of variation
  • decide on the processes that will be improved
  • gather more data ('measure') if necessary


  • propose solutions
  • carry out pilot studies, design of experiments etc. to test and evaluate the proposed solutions
  • develop an implementation plan


  • implement systems and procedures to ensure the improvements are sustained
  • develop procedures, control plans, staff training etc.
Green Belt

A member of an organization who has been trained on the improvement methodology of Six Sigma, and participates in Six Sigma process improvement projects as part of their full time job. They may either work as part of a team, led by a Black Belt, or lead smaller projects, with a Black Belt acting as mentor.

Internal Customer

In process improvement the customers can be internal or external. An internal customer is somebody in the organization to who you provide product or service. It can be anybody who relies on you to complete a task, or function, or to provide information they need to do their job.

Lean Six Sigma

An approach that combines the process improvement benefits of the Six Sigma method with the cost reduction benefits of lean manufacturing.

Little y

See "Big Y"

Project Charter

A document that summarizes the Six Sigma project, and is the basis for the official authorization, it includes:

  • details of the project team
  • the stakeholders
  • the mission statement
  • the problem statement
  • the business need
  • the scope
  • the resources, and their authorization
  • the target completion date for each phase
Six Sigma

Six Sigma is a process improvement methodology pioneered by Motorola (initiated by engineer Bill Smith, known as the 'father of Six Sigma'). It became prominent through the success of General Electric, during the tenure of CEO Jack Welch who was an advocate for Six Sigma.

The methodology uses process improvement methods, with an emphasis on statistics to achieve a quality level of better than 3.4 defects per million opportunities. Key elements are:

  • the organizational structure, including the roles of Champion. Master Black Belts, Black Belts and Green Belts
  • the DMAIC/DFSS structured problem solving approach

In its classical form, Six Sigma is a project based approach, tackling projects that will return $100,000+ savings and take several months. Many companies now use an approach that involves more, but smaller, projects, and is less statistically intensive. These are often led by Green Belts rather than Black Belts.


A display, created and maintained by the project team, that tells the story of the project. If possible it should be permanently displayed and tell the story of the project. It should follow the DMAIC process, be understandable by management, highlight questions, key learnings, issues and risks.