Zero Defect Sampling

World Conference on Quality and Improvement vol. 50 - May 1996

Abstract:Zero defect sampling is an alternative method to the obsolete Mil Std 105E sampling scheme previously used to accept or reject products, and the remaining ANSI Z1.4-1993 which is still in use. This paper discusses the development of zero defect sampling and compares it to Mil Std 105E.

Mil Std 105E accepted lots based on finding the nonconforming product of a specified acceptance quality level (AQL) no matter if it fell below the reject criteria. The sampling concept changed and the percent defective criteria for accepting or rejecting lots became less popular. New criteria calling for parts per million (PPM) quality performance requirements forced companies to reexamine the AQL sampling methodology. Zero defect sampling meets the increased performance requirements and the trend toward proactive controls such as process improvement, employee training, and integrated process appraisal. This plan is based solely on a single sample structure.

Looking ahead to the next century, global competitors must think in terms of PPM and need to consider the zero defect sampling scheme as a tool to accomplish this objective.

Keywords: Lot size - Sampling plans - Random variables - Operating Characteristic (OC) curve