Histograms

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.

Important Notes

• 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.