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Duplicate results are assessed using the relative percent difference (RPD)between duplicate <br /> measurements. If the RPD for laboratory OC samples exceeds 30 percent, data will be qualified <br /> as described in the applicable validation procedure. If the RPD between primary and duplicate <br /> field samples exceeds 100 percent for groundwater or vapor samples, data will be qualified as <br /> described in the applicable validation procedure. The RPD is calculated as follows: <br /> RPD=200 x (Xz X1)/X2+ X1 <br /> where X1 and X2 are the analytical values. <br /> 5.2.2 Accuracy <br /> Accuracy is a statistical measurement of correctness and includes components of random error <br /> (variability because of imprecision) and systematic error. It reflects the total error associated with <br /> a measurement. A measurement is accurate when the value reported does not differ from the true <br /> value or known concentration of the spike or standard. <br /> Laboratory control samples, surrogate standards, matrix spikes, and initial and continuing <br /> calibrations of instruments will be used to assess the accuracy of laboratory analyses. Laboratory <br /> accuracy is expressed as the percent recovery(%R). Accuracy limits are statistically generated by <br /> the laboratory or required by specified EPA methods. If the percent recovery is determined to be <br /> outside of acceptance criteria, data will be qualified as described in the applicable validation <br /> procedure. The calculation of%R is as follows: <br /> %R= 100 x (Xs—X)/T <br /> where X, is the measured value of the spiked sample, X is the measured value of the unspiked <br /> sample, and T is the true value of the spike solution added. <br /> Field accuracy will be assessed through the analysis of field equipment and trip blanks. Analysis <br /> of blanks will monitor errors associated with the sampling process, field contamination, sample <br /> preservation, and sample handling. The DOQ for field equipment and trip blanks is that all <br /> values are less than the reporting limit for each target constituent. If contamination is reported in <br /> Environmental/LNC/workplan/Appendix3.wpd 10 <br />