A Continuous Sampling Plan Using Sums of Conforming Run-lengths

摘要

A continuous sampling plan, CSP-SUM, is proposed based on the use of sums of run-lengths of conforming items for deciding when to switch between the phases of sampling inspection and 100% inspection. The conventional measures of performance of CSPs such as the average outgoing quality, average fraction inspected, and the proportion passed under sampling inspection are evaluated for CSP-SUM. Using these and other measures, comparisons with some standard CSPs are provided and indicate better performance for CSP-SUM. Comparisons are also made with a recently-proposed CSP utilizing CUSUMs, termed CSP-CUSUM, and indicate that the performance of CSP-SUM can be close to that of CSP-CUSUM. A table is provided to aid the choice of parameters for the operation of CSP-SUM. It is recommended that a conforming run-length control chart be maintained in parallel with CSP-SUM to detect significant upward shifts in the fraction defective of the process.