The capability of capability indices with an application to guardbanding in a test environment

The author addresses 13 cautions associated with capability indices, covering the areas of computations, assumptions, applications. and interpretations. Some recommended uses are also provided. A naive guardbanding scheme using capability indices is presented and contrasted with a more traditional approach involving a bivariate normal model. A slight modification of the traditional approach, which views consumer loss from the consumer´s point of view, is proposed. Both the capability and modified traditional approaches are applied and contrasted in a semiconductor testing example. The capability approach is shown to be more conservative than the modified traditional approach