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GES <br /> • GENESIS ENGINEERING 8 REDEVELOPMENT <br /> contaminant concentration. Accuracy will be evaluated by comparing percent recoveries to <br /> the acceptable tables in this QAPP to make sure it falls within the control limits. Control <br /> charts will be maintained for all surrogates. Also, all analytes of interest will be charted for <br /> each method for percent recovery and RSD and the charts shall be used to help show any <br /> adverse trends or drifts in the QC data, so that corrections can be made. <br /> 8.3.2 Precision (RPD/RSD) <br /> Precision is a measurement of the reproducibility of data under a specified set of conditions. <br /> For this Project,precision will be evaluated in conjunction with accuracy for the LCS <br /> samples. Precision will be determined for matrix effects using the MS/MSD samples and <br /> will be expressed as Relative Percent Difference("RPD"). <br /> RPD is defined as: <br /> RPD = (Cl - C2)x 100 % <br /> (Cl +C2)/2 <br /> • Where, Cl and C2 are the larger and smaller of the two duplicate values, respectively. <br /> Precision will be measured as the Relative Standard Deviation ("RSD") for sample and <br /> MS/MSD values. <br /> RSD is defined as: <br /> RSD = s x 100% <br /> ymean <br /> where, s = standard deviation <br /> ymeao=mean of replicate analyses. <br /> For field duplicates and replicates, both RPDs and RSDS will be used to evaluate precision. <br /> Acceptable levels of precision vary with the sample matrix, analytical method, and sample <br /> concentration. U.S. EPA precision data will be used as a basis for developing acceptance <br /> criteria for assessing precision; however, laboratory control charts must be developed and <br /> used to determine acceptance criteria for the LCS samples. <br /> • William DePaoli Property 16 of 21 <br /> Quality Assurance Project Plan <br /> February 2012 <br />