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3.3.4 Representativeness <br /> Representativeness qualitatively expresses the degree to which the sample collection <br /> and analytical protocols adequately reflect the environmental conditions present at the <br /> sampling location. If the results are reproducible, the data obtained can be said to <br /> represent the environmental condition. Representativeness is ensured by collecting <br /> sufficient numbers of samples of an environmental medium, properly chosen with <br /> respect to place and time. The precision of a representative set of samples reflects the <br /> degree of variability of the sampled medium, as well as the effectiveness of the <br /> sampling techniques and laboratory analysis. The sampling network is expected to <br /> provide data representative of the groundwater, soil vapor, sub-slab vapor, and <br /> indoor/outdoor air conditions in specific areas of concern at the Site. Representativeness <br /> in the laboratory is ensured by using the proper analytical procedures, attaining the <br /> quantitative DQOs, and meeting sample holding times. <br /> 3.3.5 Completeness <br /> Completeness is defined as the percentage of measurements made which are judged to <br /> be valid measurements. <br /> The Contract Laboratory Program (CLP) data have been found to be 80 to 85 percent <br /> complete on a nationwide basis. <br /> The percent completeness for each set of samples will be calculated as follows: <br /> Valid Data <br /> % Completeness = Total Data Planned x 100 <br /> The QA objective for completeness for all parameters will be 90 percent per matrix per <br /> analytical method. <br /> 3.3.6 Comparability <br /> Comparability expresses the confidence with which one data set can be compared to <br /> another data set measuring the same property. Comparability is ensured through <br /> consistent sampling techniques, the use of established and approved analytical methods, <br /> consistency in the basis of analysis (volume, etc.), consistency in reporting units (µg/L, <br /> µg/m3), and analysis of standard reference materials. By using standard sampling and <br /> analytical procedures, data sets will be comparable. <br /> Appendix C 10 <br />