Six Sigma is a fact-based methodology designed to improve the efficiency and effectiveness of processes. DMAIC is an acronym for the five phases used in improving existing processes: Define, Measure, Analyze, Improve and Control.
The Define phase summarizes the business problem to be solved and quantifies the impact on the customer, establishing the critical-to-quality characteristics of the process.
Measure establishes a data collection plan, gathers the data necessary to study the process and establishes the validity of the data.
Analyze looks for the root cause of defects by comparing current performance against the desired goal. Variables responsible for process variation are isolated using statistical methods and other analytic tools.
Improve determines the best way to improve the process and might include experimentation or simulation to arrive at an improvement plan.
Control creates accountability for the improved process with a control plan and, often, statistical process control (SPC) charts to ensure the variation does not return.