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I <br />larger differences resulted because one of the compounds was not <br />detected or detected at very low concentrations. At or near the <br />detection limit, very small fluctuations in quantity result in large <br />percentage differences. Concentrations near the detection limit are <br />also more vulnerable to fluctuations because the limits of linearity <br />are approached, and instrument noise and background interference <br />become greater factors. Concentrations near the detection limit would <br />thus be expected to be outside the 0 to 20 percent acceptable range of <br />reproducibility. <br />f' <br />r <br />f <br />C <br />l -1 <br />Data precision is a measure of the percent difference between the <br />ambient air concentrations of a specific constituent from a primary <br />sampler and the concentration from a co -located, duplicate sampler. <br />Since co -located duplicate samplers were not required in this work- <br />plan, data precision was not determined. <br />5.2.3 ata Completeness <br />According to the criteria specified in the Guidelines, the data set is <br />97 percent complete. Data is considered invalid if the length of <br />sample collection cannot be verified (e.g., the power is out at the <br />site), or if the sampling medium breaks during sampling or shipment <br />for analysis. <br />The approved workplan included collecting 5 gas well samples, 1 sur- <br />face walk samples, 12 ambient air samples, 6 probe samples, and <br />6 field blanks. One sample (AA -3) could not be collected for the <br />reason stated in the previous sections, therefore, resulting in <br />97 percent completeness. <br />PJ9 9390304.00D 5-10 <br />Rev. 0 09/20/88 <br />