Process Capability Indices: Heuristics for Smart Use of a Quality Metric

Process capability indices (Cp and Cpk), which represent the comparison of process variation to specification limits as a single number, are receiving increased attention in industry. A number of industries including Motorola, General Electric, Texas Instruments and Allied Signal have set goals for process capability. Existing statistical literature discusses bias, confidence intervals, and statistical limitations of the these metrics. This presentation focuses on the practical issues which arise when implementing the Cp and Cpk metrics. The question addressed herein is: “How can this quality metric be calculated in a smart, efficient manner and used to support good management decisions?”.