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' Section 17 <br /> ONSITE Environmental Laboratones Inc Recision 0 <br /> ' Quarry Assurance Plan February 15, 1996 <br /> Page 1 of 2 <br /> 17.0 ACCURACY, PRECISION AND CONIPLETENESS <br /> Precision and accuracy are two measures of reliability of an analytical result Completeness is <br /> a measure of the overall performance of the laboratory <br /> Precision is determined through duplicate analysts Accuracy is determined on spiked <br /> sample analyses and performance audit analyses Whenever accuracy, precision or <br /> completeness deviates from the goals, the source of the problem will be detemuned and <br /> corrected <br /> ' 17 1 Precision is the ability to generate the same results in repeated tests of the same <br /> sample Precision is defined as the percent relative difference (RPD) and is <br /> calculated as follows <br /> RPD _ (Original Value - Duplicate Value) X 100 <br /> (Original Value + Duplicate Value/2) <br /> Where A is the first analytical reading and B is the duplicate reading <br /> 112 Accuracy is the degree with which the obtained result agrees with the actual results <br /> Accuracy is defined in terms of percent recovery (% Rec) and is calculated from <br /> results of analyses of spike sample as follows <br /> ' % Recovery = Actual X loo <br /> Theoretical <br /> Where "Actual" is the value of the analyte found and "Theorectical" is the <br /> ' expected value based upon background concentration and the spike concentration <br /> 172 Completeness is defined as the ratio of acceptable measurements obtained to the <br /> ' total number of planned measurements <br /> ' <br /> Number Acceptable Completeness = X 100 <br /> Total Number <br /> 174 Table I lists ONSITE'seg .neral guidelines which can be used in reviewing the data <br /> and will apply to any measurement that is 5 Gimes greater than the reporting limit <br /> These criteria will not apply to extremely dirty or complex matrices or to a few known <br /> ' difficult analytes (i e , acrole[n, vinyl chlonde) <br /> Historically based accuracy limits have been set at the ONSITE laboratory and are <br /> ' updated on a regular basis These limits will supersede previous lunits established <br /> Lairuts for specific parameters can be provided upon request <br /> Word 6 0 loelsec 17 doc <br /> 1 <br />