Stages

Meaningful phases of a process, such as before and after an improvement is implemented. Stages are used to create a historical control chart that shows how a process changes over specific time periods. At each stage, Minitab recalculates the center line and control limits on the chart.

This historical chart shows three stages of a process, which represent before, during, and after the implementation of a new procedure. With stages, you can see that the process mean (centerline) and expected variation in the process (area between the upper and lower control limit) decrease over time.