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13.0 SPECIFIC ROUTINE PROCEDURES USED TO ASSESS DATA PRECISION, <br /> ACCURACY AND COMPLETENESS <br /> 13.1 QA MEASUREMENT QUALITY INDICATORS <br /> 13.1.1 PRECISION <br /> Precision will be assessed by comparing the analytical results between duplicate spike <br /> analyses. Precision as percent relative difference will be calculated as follows for values <br /> significantly greater than the associated detection limit: <br /> Precision= (D 2D 1 x 100 <br /> (Dl+D2)/2 <br /> For MS/MSD analyses: D1&D2 =MS and MSD recoveries <br /> For results near the associated detection limits, precision will be assessed based on the <br /> following criteria: <br /> Precision= original result- duplicate result I<DL <br /> DL= Detection Limit <br /> 13.1.2 ACCURACY <br /> Accuracy will be assessed by comparing a set of analytical results to the accepted or <br /> "true" values that would be expected. In general, MS/MSD and check sample <br /> recoveries will be used to assess accuracy. Accuracy as percent recovery will be <br /> calculated as follows: <br /> A-B <br /> Accuracy= C x 100 <br /> A = The analyte determined experimentally from the spike sample <br /> B = The background level determined by a separate analysis of the unspiked sample <br /> C = The amount of spike added <br /> 031090-10(4) -20- CONESTOGA-ROVERS&ASSOCIATES <br />