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%,/ <br /> 7.0 QUALITY ASSURANCE REQUIREMENTS <br /> 7.1 DATA QUALITY OBJECTIVES <br /> The quality of the data collected in the field can be adversely affected by <br /> errors in collection or observation. Establishing appropriate levels of <br /> control over sources of error and quantifying the errors, when possible, <br /> will assist in assessing the impact of errors on the project. Data quality <br /> objectives are expressed in terms of accuracy, precision, completeness, <br /> comparability, and representativeness. <br /> Accuracy is a measure of the bias in a system. Accuracy is the degree of <br /> agreement of a measurement (or an average of measurements of the <br /> same thing) with the accepted reference or true value. The exact bias of <br /> a system will never be known since the true values are not accessible. <br /> Precision is a measure of mutual agreement among individual mea- <br /> surements of the same property, usually under prescribed similar con- <br /> ditions. The measurement of precision is made through the use of du- <br /> plicate or replicate samples, taken at regular, specified intervals. <br /> Comparability expresses the confidence with which one data set can be <br /> compared with another. Comparability can be related to precision and <br /> accuracy as these quantities are measures of data reliability. <br /> Accuracy, precision, and comparability are more applicable for quantifi- <br /> able sample analyses, so for this SOP the data quality objectives will be <br /> stated in terms of representativeness and completeness. <br /> Representativeness is the degree to which a set of data accurately repre- <br /> sents the characteristics of a population, a process condition, or an <br /> environmental condition. For this SOP, representativeness will be <br /> assured by performing the sampling and observations in accordance <br /> with this procedure. <br /> Completeness a measure of the amount of valid data obtained from a <br /> measurement system compared to the amount that could be obtained <br /> under optimum conditions. For this SOP, completeness is defined as <br /> the number of samples collected compared to the number of samples <br /> planned. <br /> 7.2 AUDITS AND SCHEDULE <br /> A systems audit consists of an evaluation to determine if the compo- <br /> nents of the task have been properly selected so that the task is capable <br /> 7-1 <br />