One-sided Process Capability Assessment in the Presence of Measurement Errors

In the manufacturing industry, many product characteristics are of one-sided specifications. The well-known process capability indices CPU and CPL are often used to measure process performance. Most capability research works have assumed no measurement errors. Unfortunately, such an assumption is not realistic even if the measurement is conducted using highly sophisticated advanced measuring instruments. Therefore, conclusions drawn regarding process capability are not reliable. In this paper, we consider the estimation and testing of CPU and CPL with the presence of measurement errors, to obtain adjusted lower confidence bounds and critical values for true process capability, which can be used to determine whether the factory processes meet the capability requirement when the measurement errors are unavoidable. Copyright c © 2005 John Wiley & Sons, Ltd.