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Title: Sampling and Analysis Plan for Environmental Control Number: Revision Date: Groundwater Monitoring PUE.EN.D.026.03 10/18/2019 Page 14 of 23 Recovery= %R= ((Cs - Cu)/Cn)*100 where: Cs =Measured concentration of the spiked sample Cu= Measured concentration of the unspiked sample Cn = Nominal (theoretical) concentration increase resulting from spiking the sample, or the nominal concentration of the lab control sample. The purpose of reviewing accuracy is to ensure that the laboratories used to analyze samples collected pursuant to this SAP are accurate and meet data quality objectives. Precision Precision is defined as the agreement among a set of replicate measurements without assumption or knowledge of the true value. Precision is determined by taking the difference between two measured values and dividing by the average of the two samples to get what is known as the relative percent difference (RPD). The samples used for this assessment should contain concentrations of analyte above the laboratory's reporting limit, and may involve the use of matrix spikes. A quantifiable estimate of precision is made based on the RPD: RPD (%) = ((C1 - C2)/CA�g)*100 where: C 1 = Measured concentration of the first sample C2 =Measured concentration of the sample duplicate/replicate CAvg=Average of the two concentrations. RPD and comparison criteria are described in Section 5.2.1. 5.2 Data Review, Validation and Verification Requirements Field and laboratory results are reviewed and validated in accordance with the specifications presented in this section. Analytical results are electronically entered into the database or data tables when possible to eliminate transcription errors. Hand entered results are proofed, as necessary, by data validation personnel to address the potential for transcription errors. 5.2.1 Data Validation Analytical data are validated and verified to assess how well the data satisfy data quality objectives for accuracy, precision and completeness specified by this SAP and the analytical laboratory. Conditions requiring the invalidation of analytical data are rare, as noted in the following sections. However, conditions necessitating qualifying (flagging) data in the data transmittal are more common and will be evaluated based on the following criteria. Qualified data are valid and usable in every way, but are flagged to alert the user that special care may apply to their use in interpretations.