DMAIC - Five step process (Define-Measure-Analyze-Improve-Control) for understanding and driving out variation from a process. 

DFSS (Design for Six Sigma) - Approach of “building quality” and “process control” in at the design, or re-design, stage of product or process development where the expected outcome is at least 4.5 sigma performance.

DOE - (Design of Experiment) is a structured, organized method for determining the relationship between factors (Xs) affecting a process and the output of that process (Y).