Lot-dependent sampling plans for qualifying long-term production capability with a one-sided specification

Abstract

Acceptance sampling plan establishes a required sample size for lot inspection and decisive capability criteria for lot dispositions. The multiple-lot dependent state (MDS) and the generalized MDS (GMDS) plans have been recently developed for operating capability-qualified compliance testing of a process with a one-sided specification in continuous submissions. However, both lot-dependent plans are incapable for sustaining a long-lasting supplier-buyer relationship. The MDS plan’s benefits deteriorate as the number of deliberated anteceding lot-sentencing outcomes increases; the GMDS plan may suffer a schematic problem in some cases where the current lot having marginal capability will be accepted with an inferior capability history. To remedy those shortcomings, an adjustable MDS (AMDS) sampling plan on qualifying the process capability with a one-sided specification is constructed. This AMDS plan not only allows more backtracking lots encompassed in the lot-disposition decision but also substantially improves the inspection efficiency regarding the required sample size and lot-discriminatory power. More importantly, the plan, operating for the long-run inspection, exhibits a consistent upward-trend phenomenon for the required acceptance-capability standard, which firmly advocates the sustainability of business whose suppliers show continuous improvement of process capability. Finally, the industrial applicability of AMDS is illustrated in a case study.