The Process Capability charts provide an indication of the performance of a process. The Process Capability chart provides a graphical comparison of the distribution of a characteristic to its specification limits. It depicts where a process is targeted in relation to nominal and the spread of the process in relation to the specification tolerance limits.

Use of the Process Capability Chart

• To determine where a process is positioned in relation to the nominal specification for a characteristic.
• To determine the spread of a process in relation to the tolerance limit specifications for a characteristic.
• To estimate the percentage of the actual distribution which is outside of the tolerance limits. This provides an indication of the amount of defectives which would be produced.
• To estimate the percentage of the shifted distribution outside of the tolerance limits. This provides an indication of the amount of detectives which would be produced if the distribution is centered at nominal.
• Monitor the capability of a process over time.
• Predicting whether a process can meet specifications.
• Observing the effects of adjustments made to a process.