Causal theory, in Six Sigma terms, means that you create output (y) from an input (x) and a function (f). Clear as mud so far? Don’t worry.
The Control phase is the fifth and last phase of a DMAIC process. The main activity in the Control phase is to control the improved process.
Maintaining solutions is one of the key activities in the Control Phase to ensure the new process is implemented and doesn’t revert.
The multi-vari chart shows you variation by separating it into three possible sources (within-piece, piece-to-piece, and time-to-time.)
Response surface modeling is a mathematical and statistical technique useful for developing, improving, and optimizing the process.