Six Sigma is a methodology that relies on data and is centered around process improvement by identifying and eliminating the sources of defects (errors) and reducing inconsistencies in production and business procedures. Its primary goal is to reach a quality level where only 3.4 defects occur per million opportunities (DPMO). This method requires processes to operate at a six standard deviation (σ) level from the mean, signifying exceptionally high performance and efficiency.

It employs a structured approach, often the DMAIC (Define, Measure, Analyze, Improve, Control) framework, to methodically tackle issues. Companies like Motorola and General Electric championed its use, making it a critical tool for achieving cost reduction and significantly increasing customer satisfaction.