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What is Six Sigma?

Six Sigma is a process improvement methodology that has been used across almost all industries for more than 25 years. Developed for manufacturing at Motorola and made popular by Jack Welch and General Electric, Six Sigma is a rigorous and statistically-driven approach to quality improvement, cost reduction, and business performance.

Six Sigma has its roots in statistical methods and earlier Total Quality Management (TQM) practices. Six Sigma is often combined with Lean, in practice, under the banners of “Lean Sigma” or “Lean Six Sigma” since they are both data-driven, systematic improvement methods and there is overlap in the use of basic statistical methods.

Typically, formal Six Sigma projects are run by specially-trained and formally-certified “Belts,” such as Green Belts, Black Belts, or Master Black Belts using one of two frameworks called DMAIC and DMADV. These methodologies are both used to eliminate defects through data intensive approaches.


This methodology is best put to use when a product or process currently exists at the company, but fails to meet performance expectations or otherwise leaves customers unsatisfied.

DMAIC stands for:

  • Define:  The goals of the project and the customer deliverables

  • Measure:  The current performance of the process

  • Analyze:  The defects to find the root cause

  • Improve:  The process, generally by resolving defects

  • Control:  The performance of future processes



This methodology is best put to use when either the existing product or process has already been optimized, yet still does not meet the customer’s requirements, or there is no existing product or process within the company, and one must be developed.

DMADV stands for:

  • Define:  The goals of the project and the customer deliverables

  • Measure:  And determine the needs of the customer

  • Analyze:  The options to meet the customer’s requirements

  • Design:  A detailed process for meeting the customer’s requirements

  • Verify:  The performance and ability of the design



Corrective and Preventative Action (CAPA) systems often serve as the foundation of Six Sigma and other cost reduction and process improvement efforts. This practice allows the leaders of an organization to access many aspects of daily business processes and adjust various factors with the intention of improving overall business productivity.


How does CAPA work?

CAPA brings about improvements to an organization’s processes, driven by the desire to remove causes of deficiencies or other undesirable situations; these actions can be reactive, hence Corrective Action, or preemptive, Preventative Action. The success of CAPA implementation is largely dependent on an understanding of performance indicators, as well as the ability to use those indicators to identify performance non-conformities.

The purpose of the CAPA system is to function as a feedback loop, identifying and investigating quality problems. It aims to correct nonconforming products and other qualities problems, while preventing re-occurrence of those issues and eliminating the potential causes of potential issues.


What are the CAPA management controls?

  1. Design Control, in which design changes are managed and documented in response to deficiencies or product improvements, and product design is moved to production.
  2. Production & Process Control, in which the latest product design is to be perfectly reproduced.

  3. Material Controls

  4. Equipment & Facilities Control

  5. Records, Documents, & Change Control


Where does the CAPA system get its input?

  1. Repetitive or critical non-conformities

  2. Process Issues

  3. Equipment Issues

  4. Audits or complaints

  5. Incomplete or deficient procedures