Which phase of Six Sigma tests and verifies root causes?

The Define phase focuses on identifying the problem, setting goals, and outlining the project scope. It establishes the framework for the Six Sigma project but does not involve testing or verifying root causes. Instead, it sets the stage for further analysis by gathering initial data and understanding customer needs.

The Control phase is implemented after improvements have been made to ensure that the gains are sustained over time. It involves monitoring the processes and establishing control systems but does not engage in root cause analysis. Its primary goal is to maintain the improvements and prevent regression to previous performance levels.

In the Improve phase, teams develop solutions to address the root causes identified during the Analyse phase. While it involves implementing changes, it does not focus on testing or verifying those root causes. Instead, it is about optimizing processes based on the insights gained during analysis.