Evaluation of procedures for quality assurance specifications

9800742004Final reportKopac, Peter A.PDFTech ReportFHWA-HRT-04-046DTFH61-98-C-00069PavementsQuality assuranceStatistical quality controlAcceptance samplingTurner-Fairbank Highway Research CenterBurati, J. L.Weed, R. M.Hughes, C. S.Hill, H. S.Clemson University. Dept. of Civil EngineeringUnited States. Federal Highway Administration. Office of Research, Development, and TechnologyTurner-Fairbank Highway Research CenterNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceNTL-HIGHWAY/ROAD TRANSPORTATION-DesignFederal Highway AdministrationThe objective of this project was to develop a comprehensive quality assurance (QA) manual, supported by scientific evidence and statistical theory, which provides step-by-step procedures and instructions for developing effective and efficient QA specifications. This technical report summarizes the steps taken to accomplish this goal, along with the analyses that were conducted to support the recommendations made in the QA manual (FHWA-RD-02-095). The analytical techniques used depended on the decision that needed to be made. Both analytical and computer simulation approaches were used. Percent within limits (PWL) [or its complement, percent defective (PD)] was selected as the best quality measure because it combines both the sample mean and standard deviation into a single measure of quality. An approach based on a single composite quality measure derived from a general performance model to predict expected pavement life was developed and is the recommended approach for determining payment factors when multiple quality characteristics are measured. A detailed discussion and analysis are also presented regarding the risks involved in the various approaches to verifying the contractor's test results. The relatively high risks that are associated with typical agency verification testing frequencies are highlighted