Capability Evaluation of a Product Family for Processes of The Larger-the-Better Type

Process capability indices (PCIs) have been widely used in manufacturing industry, but most of the studies associated with analysing the quality and efficiency of a process are limited to discussing one single quality specification. Practically, a product family is usually composed of several models, which result in different specifications. Generally, the quality characteristics of a product can be classified into three types; the nominal-the-best, the smaller-the-better and the larger-the-better types. This paper introduces one simple and applicable method to evaluate the process capability of a product family. The process is of the larger-the-better type and consists of several models with different specifications. For practical applications, a simple step-by-step procedure is established to determine whether the total process capability of the product family meets the preset target. Finally, an example is given and a procedure for a hypothesis test is provided for easy application.