A new Spk -based sample-size tightening sampling system for lot determination

ABSTRACT This article presents a new Spk-based sample-size tightening sampling system by variables inspection for lot determination when the quality characteristic has bilateral specification limits. The proposed system has a flexible switching mechanism between normal and tightened inspection, which is adaptively employed for the occurrence of quality deterioration in submitted lots. The performances of discriminatory power, economy and sensitivity to quality shift of the proposed method are demonstrated by comparing the operating characteristic (OC) curve, average sample number (ASN) and average run length (ARL), respectively, with the existing sampling plans. Furthermore, for practical application, the solved plan parameters under certain quality conditions are tabulated for quick reference, and an example taken from the Multi-layer Ceramic Capacitor (MLCC) industry is studied for illustration.