Name two common process-capability indices other than Cp and Cpk.

Name two common process-capability indices other than Cp and Cpk.

• A. Pp and Ppk
• B. Cp and Cr
• C. Pp and Cp
• D. Cpm and Ppk

Answer: (A)

Understanding process-capability indices helps you judge how well a process meets specifications. Cp and Cpk are the usual short-term indices that look at the spread and centering within a sample of data. The two commonly used indices that address long-term performance are Pp and Ppk. Pp uses the overall process variation (the total spread across all data) relative to the tolerance width, giving a sense of what the process could achieve across time. Ppk takes that same overall variation and looks at how far the process mean is from the nearest specification limit, capturing whether the process is centered over the long run. In short, Pp and Ppk reflect long-term capability, complementing Cp and Cpk.

Understanding process-capability indices helps you judge how well a process meets specifications. Cp and Cpk are the usual short-term indices that look at the spread and centering within a sample of data. The two commonly used indices that address long-term performance are Pp and Ppk. Pp uses the overall process variation (the total spread across all data) relative to the tolerance width, giving a sense of what the process could achieve across time. Ppk takes that same overall variation and looks at how far the process mean is from the nearest specification limit, capturing whether the process is centered over the long run. In short, Pp and Ppk reflect long-term capability, complementing Cp and Cpk.