Six sigma refers to a set of strategies, processes, and quality checks that ensure a high standard of quality for the products produced. Motorola originally developed six sigma in 1985.¹ However, six sigma only became famous after Jack Welch made it a central focus business strategy at General Electric in 1995.¹ The term six sigma originated from manufacturing terminology, especially terms associated with statistical analysis and modeling.¹
Generally, six sigma aims to improve the quality of process outputs by removing the causes of defects in manufacturing and business processes. It does this through using a set of quality management methods, including statistical methods. Each six sigma project follows a sequence of steps and has quantified value targets. Examples may include: process cycle time reduction, customer satisfaction, reduction in pollution, and cost reduction.²
A manufacturing process can be described by a sigma indicating the amount of defect-free products manufactured. 99.99966 percent of products manufactured need to be statistically defect-free to be represented by a sigma, which equates to just 3.4 defects per million manufactured.²
There are two project methodologies used by managers to implement six sigma: DMAIC and DMADV. DMAIC stands for: define the problem, measure key aspects of the current process, analyze data to investigate cause-and-effect relationships, improve current processes using mistake proofing and design experiments, and finally control future processes to ensure deviations are corrected.³ DMADV includes defining design goals, measuring characteristics critical to quality, analyzing to develop and design alternatives, designing an improved alternative, and verifying the design and implementing it.³
Six sigma involves the professionalizing of quality management functions, where before it was in the hands of the production floor and statisticians. There are five different roles that individuals can take in the six sigma system: leadership, champions, master black belts, black belts, and green belts. Executive leadership is responsible for setting up the vision for six sigma implementation.³ Champions take responsibility for six sigma implementation, while master black belts act as in-house coaches and devote 100 percent of their time to six sigma.³ Black belts apply six sigma to specific projects and green belts are employees who take up six sigma along with continuing their other job responsibilities.³
1. “The Inventors of Six Sigma.” Archived from The Original on November 6, 2005.
2. Antony, Jiju. “Pros and cons of Six Sigma: an academic perspective.” Archived from The Original on July 23, 2008.
3. Schroeder, Richard. (2000). Six Sigma. Random House Inc.