TRB’s National Cooperative Highway Research Program (NCHRP) Web-Only Document 114: Precision Estimates for AASHTO Test Method T 269 Determined Using AASHTO Materials Reference Laboratory (AMRL) Proficiency Sample Data explores the use of data from the AMRL Proficiency Sample Program (PSP) to update precision estimates for the American Association of State Highway and Transportation Officials (AASHTO) Standard Test Method T269, Percent Air Voids in Compacted Dense and Open Asphalt Mixtures.