Integrated QSS-RS plans based on the process yield index for lot acceptance determination

Abstract

Acceptance sampling plans based on the process yield indices have been adopted in the inspection of outgoing and incoming lots when the required fraction defective is very low. To achieve this aim and increase their overall efficiency and flexibility, various sampling plans have been constructed for different purposes using numerous methods. In practice, resubmitted sampling (RS) plan encourages suppliers to work harder to produce better quality products that pass the first inspection. Besides, the concept of switching inspection rules, which can provide a flexible sampling procedure and reducing the required sample size for inspection, is especially useful when the inspection is costly or destructive. This paper proposes integrated sampling plans by considering the merits of the process yield index S_pk, RS, and switching inspection rules for controlling lot fraction nonconforming when the quality characteristic is normally distributed with two specification limits. The performance of the proposed plans is investigated and the results indicate a satisfactory performance of the proposed plans. Besides, the advantages of the proposed plans over the existing plans are discussed. Finally, real data from the spark plug industry are used to illustrate the implementation.

Keywords:

• Acceptance sampling plan
• lot resubmission
• switching inspection rules
• operating characteristic curve
• process yield index