The Quality Measurement Plan (QMP)

This paper describes the Quality Measurement Plan (QMP), a recently implemented system for reporting the qualify assurance audit results to Bell System management, QMP replaces the T-rate system, which evolved from the pioneering statistical work of Shewhart and Dodge during the 1920's and 1930's at Bell Laboratories. Box and whisker plots are used for graphically displaying confidence intervals for the quality of the current production. The confidence interval is computed from both current and past data and is derived from a new Bayesian approach to the empirical Bayes problem for Poisson observations. Here we discuss the rationale, mathematical derivations, dynamics, operating characteristics, and many comparative examples. We show that QMP reduces statistical errors relative to the earlier T-rate system.