Methods for Quality-Assurance Review of Water-Quality Data in New Jersey

This report is an instructional and reference manual that describes methods developed and used by the U.S. Geological Survey (USGS), New Jersey District, to assure the accuracy and precision of the results of analyses of surface- and ground-water samples received from analyzing laboratories and, ultimately, to ensure the integrity of water-quality data in USGS databases and published reports. A statistical-analysis computer program, COMP.PPL, is used to determine whether the values reported by the laboratories are internally consistent, whether they are reasonable when compared with values for samples previously collected at the same site, and whether they exceed applicable drinking-water regulations. The program output consists of three files -- QWREVIEW, QWOUTLIERS, and QWCALC. QWREVIEW presents the results of tests of chemical logic and shows values that exceed drinking-water regulations. QWOUTLIERS identifies values that fall outside the historical range of values for the site sampled. QWCALC shows values and calculations used for reference purposes. Prepared in cooperation with the New Jersey Department of Environmental Protection.