Trend control of a group of multiple failure rates, which has between and within lots variation

摘要

It is not effective to use a usually applied p-control chart when the variation between and within groups of multiple failure rates is large. For such a case, we present a new method of controlling failure rates properly by using logit transformation and inverse sine transformation so as to transform an attribute value to a measurable value and by applying an x - Rs control chart and an x - s control chart to a measurable value.