Decomposition of aggregate defective rate in batch production

In batch/short run production, changes in product-mix (or inter-product demand) can have a significant impact on the overall process defective rate, but this effect is often neglected in process quality analysis. This paper describes the use of a decomposition technique to single out this effect and the effect associated with changes in real process performance. The technique allows both effects to be expressed in indices which conveniently summarize information in a more concise and usable form. The results of an application study using a set of batch/short-run production data are presented.