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Statistical procedures for determination and verification of minimum reporting levels for drinking water methods

机译：确定和验证饮用水方法最低报告量的统计程序

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The United States Environmental Protection Agency's Office of Ground Water and Drinking Water has developed a single-laboratory quantitation procedure: the lowest concentration minimum reporting level (LCMRL). The LCMRL is the lowest true concentration for which future recovery is predicted to fall, with high confidence (99%), between 50% and 150%. The procedure takes into account precision and accuracy. Multiple concentration replicates are processed through the entire analytical method and the data are plotted as measured sample concentration (y-axis) versus true concentration (x-axis). If the data support an assumption of constant variance over the concentration range, an ordinary least-squares regression line is drawn; otherwise, a variance-weighted least-squares regression is used. Prediction interval lines of 99% confidence are drawn about the regression. At the points where the prediction interval lines intersect with data quality objective lines of 50% and 150% recovery, lines are dropped to the x-axis. The higher of the two values is the LCMRL. The LCMRL procedure is flexible because the data quality objectives (50-150%) and the prediction interval confidence (99%) can be varied to suit program needs. The LCMRL determination is performed during method development only. A simpler procedure for verification of data quality objectives at a given minimum reporting level (MRL) is also presented. The verification procedure requires a single set of seven samples taken through the entire method procedure. If the calculated prediction interval is contained within data quality recovery limits (50-150%), the laboratory performance at the MRL is verified.
机译：美国环境保护局的地下水和饮用水办公室制定了单一实验室的定量程序：最低浓度最低报告水平（LCMRL）。 LCMRL是预计未来回收率将下降的最低真实浓度，其高置信度（99％）在50％至150％之间。该过程考虑了精度和准确性。通过整个分析方法处理多个浓度重复样品，并将数据绘制为测得的样品浓度（y轴）与真实浓度（x轴）的关系。如果数据支持在浓度范围内恒定方差的假设，则绘制一条普通的最小二乘回归线；否则，使用方差加权最小二乘回归。绘制了关于回归的置信度为99％的预测区间线。在预测间隔线与50％和150％恢复的数据质量目标线相交的点处，这些线下降到x轴。这两个值中的较高者是LCMRL。 LCMRL程序具有灵活性，因为可以更改数据质量目标（50-150％）和预测间隔置信度（99％）以适合程序需求。 LCMRL确定仅在方法开发期间执行。还介绍了在给定的最低报告级别（MRL）下验证数据质量目标的更简单程序。验证过程需要整个方法过程中的一组七个样本。如果计算出的预测间隔包含在数据质量恢复限制内（50-150％），则将验证MRL的实验室性能。

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