What is Six Sigma?

Since its inception at Motorola in 1980s, Six Sigma has grown to represent several key concepts including a management philosophy, business strategy, methodology, metric, and set of tools and techniques for achieving breakthrough improvements. Six Sigma starts with the premise that every facet of clinical, academic, research, and business operations is a process with discrete steps and that all processes have a certain level of variation. The ultimate goal of Six Sigma is to achieve zero defects by driving undesirable variation out of the system. General Electric, Samsung Electronics, Honeywell International, and many other manufacturing organizations have adopted rigorous, data-driven and customer-focused Six Sigma methodology to deliver defect-free products and services, reduce cost of poor quality (COPQ), increase capacity, and improve their business results. A growing body of evidence suggests that Six Sigma can be successfully applied in healthcare and other service organizations to improve process capability, increase patient satisfaction, and improve quality while decreasing operating costs. Successful implementation of Six Sigma in any type of organization requires visible management commitment, clear linkage of Six Sigma projects to strategic goals and customer needs, consistent use of accurate, valid and reliable data to support decision making, defined expectations, accountabilities, roles, and responsibilities, effective communication strategies, robust infrastructure, and technical expertise in Six Sigma.

The term sigma (σ) is a Greek letter that refers to the standard deviation or measure of variation in a process. Processes with minimal variation or higher sigma quality levels are less likely to produce defects. If a process operates at the Six Sigma level it means that this distinctly capable process is almost perfect and 99.99966% of resulting products and services are free of defects. This world-class performance equates to only 3.4 defects per million opportunities (DPMO). In a normally distributed process, 99.99966% will actually fall within ±4.5 sigma. However, it is recognized that over time processes may shift as much as ±1.5 sigma from their target value, and in order to produce no more than 3.4 defects per million opportunities specification limits have to be set at ±6 sigma. Most organizations operate at three or four sigma level and achieving Six Sigma level of performance requires a significant cultural shift. Although processes capable of producing 99% products and services free of defects may seem adequate, they are not always good enough in high risk industries.

Normal Distribution Shifted