Six Sigma is a process improvement methodology that focuses on reducing defects and increasing quality, as defined by customers. The most common technique in Six Sigma is DMAIC, which is a five-step systematic approach to managing a process improvement project. The goal is to identify problems that do not have obvious solutions, determine their root causes and implement lasting solutions. The steps are Define, Measure, Analyze, Improve and Control. DMAIC projects are typically conducted by Six Sigma Green Belts or Black Belts.
The goal of the Define phase is to understand the problem, by clarifying the high-level process, establishing the customer expectation of quality and determining the existing performance relative to that expectation.
In the Measure phase, the project team creates a detailed process map showing how the process is performed and gathers detailed data on the problem.
The main objective of the Analyze step is to uncover the root causes of the process performance problem. Potential root causes are validated with data.
In the Improve phase, solutions that counter the root causes are tested and implemented.
The Control phase includes components to ensure that the gains obtained in the Improve phase are sustained. They include documentation, training and a plan for process monitoring.
Tools for DMAIC projects include Pareto charts, control charts, fishbone diagrams, process maps, descriptive statistics and advanced statistical analysis.