What It Is Used For
- To display variable data so that the pattern of variation can be identified.
When to Use It
- To help determine if there are special causes of variation present in the process.
- To compare the output of the process with customers’ specifications.
- A nearly normal distribution is an indication that the process has mainly common cause variation present.
- A bi-modal or multi-modal distribution is almost always a sign of a special cause of variation in the process or in the data collection technique.