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Six Sigma – Definition

Six Sigma Definition

Six Sigma (often abbreviated as 6σ) is a statistical-based quality-control program that emphasizes on the reduction or elimination of defects in a product, a process or a service through the application of  certain process-improvement techniques and tools. Introduced by Bill Smith of Motorola, Inc in the mid-1980s, Six Sigma employs a data-driven approach that ensures that at least 99.99966% (or 3.4 parts per million) of all products, processes or services are defect-free. Over the years, the Six Sigma process has evolved to encompass various business-management strategies such as:

  • Meeting customer requirements.
  • Boosting customer retention.
  • Refining and perpetuating products and services.
  • Reducing costs and increasing profits.

Virtually all industries come under the scope of Six Sigma. There are several organizations that are involved in Six Sigma training and conferring certifications such as yellow belts, green belts and black belts.

A Little More on What is Six Sigma

Six Sigma employs a disciplined statistical approach to effect improvements in a manufactured product, a business process or a commercial service. Although developed by Motorola in the mid-1980s, Six Sigma was enthusiastically adopted by General Electric (GE) by the early 1990s under the leadership of Jack Welch. At present, thousands of businesses, especially those that typically employ statistics, financial analysis and project management to achieve better business performance, have already integrated Six Sigma methodologies into their business strategies.

The USP of Six Sigma is its emphasis on qualitative measurements of success over qualitative markers. Six Sigma has evolved into a comprehensive quality-control process with three distinct roles:

    1. Role 1 – Statistical Benchmark: Six Sigma has laid down certain ground rules that a business process must follow in order to be certified as efficient. According to the benchmarks set by Six Sigma, a business must ensure that at least 99.99966% (or 3.4 parts per million) of all products, processes or services are free from defects.


  • Role 2 – Training Initiative: Six Sigma provides training and certification programs to businesses that are interested in implementing the core principles of the doctrine. Six Sigma offers multiple levels of certification, starting with the basic white belt and culminating in the black belt.
  • Role 3 – A Process-improvement Philosophy: Six Sigma is a process-improvement philosophy that is applicable to all businesses and processes.


Six Sigma Methodologies

There are two distinct methodologies that Six Sigma projects can follow – DMAIC and DMADV (DFSS). Both methodologies comprise five phases each.


This methodology is utilized by projects that are formulated to upgrade existing processes. Its five phases are described as follows:

  1. Define: This phase defines the customers, their requirements and their expectations.
  2. Measure: This phase measures the performance of the core business processes.
  3. Analyze: This phase analyzes collected data and process maps to discover the underlying causes of defects and identify areas of improvement.
  4. Improve: This phase involves designing innovative solutions to improve the target process.
  5. Control: This phase involves controlling the new implementations and avoiding any regressions.


This methodology, also known as DFSS (“Design For Six Sigma”), is utilized by projects that are involved in creating new product or process designs. The following are the five phases of this approach:

  1. Define: This phase defines the design goals keeping in mind the interests of both the organization as well as its stakeholders.
  2. Measure: This phase measures characteristics that are critical to quality (CTQ). It also measures and reassesses risk and estimates product potential and capacity of the production process.
  3. Analyze: This phase provides design alternatives. It includes several steps such as creating and evaluating conceptual designs and developing the best possible design keeping in mind the the total life cycle cost of the design.
  4. Design: This phase involves creating a detailed design of the improved alternative.
  5. Verify: This phase verifies and validates the improved alternative design. This is followed by deployment of the new process, together with detailed documentation of all vital knowledge gained during the process.

References for Six Sigma

Academic Research on Six Sigma

Six Sigma: The breakthrough management strategy revolutionizing the world’s top corporations, Alexander, M. (2001). GE, Motorola, and AlliedSignal pioneered a breakthrough management program that they termed Six Sigma. Six Sigma has revolutionised fiscal performance in the corporate world. It is a highly efficient breakthrough management tool that assists businesses in increasing market share, reducing costs and augmenting bottom line profitability. Major corporations across the world have implemented Six Sigma, irrespective of the industry that they cater to.

Six Sigma: a goal-theoretic perspective, Linderman, K., Schroeder, R. G., Zaheer, S., & Choo, A. S. (2003). Journal of Operations management, 21(2), 193-203. The authors highlight certain shortcomings of the Six Sigma process, such as the lack of a theoretical foundation as well as limited usability in research. This paper scrutinizes Six Sigma from a goal-theoretic perspective and identifies certain propositions for future research. The authors suggest using their findings as a basis for further scientific analysis of the Six Sigma phenomenon.

Benefits, obstacles, and future of six sigma approach, Kwak, Y. H., & Anbari, F. T. (2006). Technovation, 26(5-6), 708-715. This paper scrutinizes the evolution, strengths and shortcomings of the Six Sigma process and lists out the various determinants of a successful Six Sigma implementation. The authors leverage their experiences with several successful Six Sigma projects to suggest additional improvements to the management approach. The paper concludes that with due commitment, it is possible for an organization to embrace the cultural changes prescribed by Six Sigma, that will lead it on the path of financial success.

Six Sigma: a breakthrough strategy for profitability, Harry, M. J. (1998). Quality progress, 31(5), 60. The author describes Six Sigma as an aggressive campaign that is intended to increase profitability and market share, and enhance customer satisfaction levels of a business. Six Sigma offers several statistical tools and prescribes certain interventions that help an organization achieve breakthrough profitability as well a dramatic increase in quality levels.

Six Sigma: Definition and underlying theory, Schroeder, R. G., Linderman, K., Liedtke, C., & Choo, A. S. (2008). Journal of operations Management, 26(4), 536-554. In this paper, the authors employ a theoretical approach, using available documentation, to define and explain the concept of Six Sigma. The paper studies the quality-focused organizational structure prescribed by the Six Sigma approach and outlines its merits in not only effecting improvements in processes but also in enabling problem exploration within the organization.

Key ingredients for the effective implementation of Six Sigma program, Antony, J., & Banuelas, R. (2002). Measuring business excellence, 6(4), 20-27. The authors outline the principal constituents of a successful Six Sigma implementation, based on a survey conducted in various manufacturing as well as service-based industries in the UK. The paper emphasizes the importance of gaining a proper understanding of the various factors that are critical to the successful implementation of a Six Sigma project.

The integration of lean management and Six Sigma, Arnheiter, E. D., & Maleyeff, J. (2005). The TQM magazine, 17(1), 5-18. This paper seeks to address the various misconceptions regarding both lean management and Six Sigma by performing a thorough analysis of both systems and outlining the various concepts and methodologies involved in their implementation. The authors then proceed to describe the mutual benefits that can be derived when organizations implementing lean management and organizations implementing Six Sigma collaborate with each other.

Lean production, six sigma quality, TQM and company culture, Dahlgaard, J. J., & Mi Dahlgaard-Park, S. (2006). The TQM magazine, 18(3), 263-281. This paper evaluates the concepts and outcomes of lean production and then performs a comparison of the lean production philosophy with both the six sigma quality process as well as the underlying concepts of total quality management (TQM). The paper concludes with a discussion about incorporating these management principles and philosophies into the company culture.

Six sigma for service processes, Antony, J. (2006). Business Process Management Journal, 12(2), 234-248. This study is an attempt at illustrating the huge potential of Six Sigma as a statistical-based approach to improve product and service quality and enhance process performance. The author demonstrates the fundamental attributes of Six Sigma and attempts to elucidate the procedures that are involved in applying the concept to service operations. The author also demonstrates how Six Sigma differs from other quality management initiatives such as total quality management (TQM) and goes on to identify the limitations of the Six Sigma model.

Some pros and cons of six sigma: an academic perspective, Antony, J. (2004). The TQM magazine, 16(4), 303-306. This article emphasizes on the advantages as well as drawbacks of Six Sigma from a purely academic standpoint. Continued evolution of the Six Sigma process has brought about drastic changes to its overall structure over the several years since its conceptualization. However, its core principles will continue to survive and grow. Nevertheless, the author highlights the lack of a theoretical foundation of the process and hence, urges academicians to reduce the discrepancies that exist between theoretical understanding and practical application of the concept.

Successful implementation of Six Sigma: benchmarking general electric company, Henderson, K. M., & Evans, J. R. (2000). Benchmarking: An International Journal, 7(4), 260-282. This paper scrutinizes the fundamental principles inherent to Six Sigma, and analyzes the merits of the business management philosophy, while underlining the effectual approaches for its implementation. The authors evaluate the achievements of the General Electric Company in successfully implementing the Six Sigma process. The paper concluded that an effective implementation of Six Sigma necessitates an absolute backing as well as participation of higher management, organizational infrastructure, facilities for training, analytical tools, and access to human resources‐based activities.

Critical success factors for the successful implementation of six sigma projects in organisations, Coronado, R. B., & Antony, J. (2002). The TQM magazine, 14(2), 92-99. The paper scrutinizes available research documents pertaining to the factors that determine the successful implementation of a Six Sigma process in various organizational processes. These documents have elaborately demonstrated how numerous businesses have derived notable benefits from implementing a statistically-oriented approach to process and product quality improvement. Introduced by Motorola in the later part of the 20th century, Six Sigma has evolved from a quality performance measurement tool into a potent business management philosophy.

Process management and the future of six sigma: savvy companies have learned that their sixsigma initiatives must serve the larger endeavor of process …, Hammer, M. (2002). MIT Sloan management review, 43(2), 26-33. The paper explains how process management drastically changes management systems and highlights the importance of absolute commitment from management executives. The author explains that successful implementation of a Six Sigma process will not only bring about cost savings, but will also accelerate the development of new products while maintaining higher levels of both customer satisfaction as well as profitability.

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