Six-Sigma refers to a quality improvement and business strategy concept started by Motorola, USA in 1986.  In statistical terms, Six-Sigma is the abbreviated form of 6 standard deviations from the mean. Six-Sigma is a set of methodologies used by businesses to achieve extremely low failure rates in any process. It provides the techniques and tools to improve the capability and reduce the defects in any process.

Each Six Sigma project carried out within an organization follows a defined sequence of steps and has quantified financial targets (cost reduction or profit increase). A six sigma process is one in which 99.99966% of the products manufactured are statistically expected to be free of defects (3.4 defects per million opportunities or 3.4 DPMO).

Six Sigma projects follow two methods inspired by Deming's Plan-Do-Check-Act Cycle.


Define the problem.

Measure key aspects of the current process.

Analyze the data to investigate and verify cause-and-effect relationships.

Improve the current process based upon data analysis using techniques.

Control the future state process to ensure that there is no deviations from target.


Define design goals that are consistent with customer demands.

Measure and identify CTQs (characteristics that are Critical To Quality).

Analyze to develop and design alternatives.

Design details, optimize the design, and plan for design verification.

Verify the design, set up pilot runs, implement the production process and hand it over to the process owner(s).

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