Use Capability Sixpack - Normal to assess the capability of an in-control process when the data are normally distributed or Box-Cox transformed. A capable process is able to produce products or services that meet specifications.

The process must be in control before you assess capability. If the process is not in control, then the capability estimates will be incorrect.

The normal Capability Sixpack provides a table of capability statistics and tools to determine whether the process is in control and the data are normally distributed.

An engine manufacturer uses a forging process to produce piston rings. The forging process is in control, and now the quality engineers want to assess the process capability. From the 5 measurements of the inner piston ring diameter, 25 samples were collected. The specification limits for piston ring diameter are 74.0 + 0.05.

Data source: Douglas C. Montgomery (1996). Introduction to Statistical Quality Control. John Wiley & Sons, New York.

Data: Piston.MTW (available in the Sample Data folder).