Analysis of environmental data with censored observations
Analysis of environmental data with censored observations
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DOI：
10.1021/es960695x
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发表时间：
1997-12-01
影响因子：
11.4
通讯作者：
Meeker, WQ
中科院分区：
文献类型：
--
作者：
Liu, SP;Lu, JC;Meeker, WQ
环境污染对人类以及陆地和水生生态系统的潜在威胁可能取决于不同化学品的浓度总和。然而，直接汇总环境数据一般不可行，因为通常记录的某些化学品浓度低于分析报告限值。这在数据分析中产生了特殊的问题。提出了一种新的模型选择方法--前向截尾回归，用于环境数据截尾情况下的模型选择。通过使用来自美国地质调查局先前进行的研究的数据，使用美国中西部地下水中阿特拉津（2-氯-4-乙氨基-6-异丙基氨基-s-三嗪）、脱乙基阿特拉津（DEA，2-氨基-4-氯-6-异丙基氨基-s-三嗪）和脱异丙基阿特拉津（DIA，2-氨基-4-氯-6-乙氨基-s-三嗪）的浓度证明了该程序。本研究中每种化合物超过80%的观察结果在0.05 μ g/L下删失。阿特拉津、DEA和DIA的删失观测值用选定的模型进行插补。阿特拉津残留的总和（阿特拉津+ DEA + DIA），然后可以使用观察值和插补值的组合来计算，以生成伪完整的数据集。将所有子集回归程序应用于伪完全数据以选择阿特拉津残留的最终模型。所提出的方法可用于分析类似的情况下，环境污染的删失数据。
The potential threats to humans and to terrestrial and aquatic ecosystems from environmental contamination could depend on the sum of the concentrations of different chemicals. However, direct summation of environmental data is not generally feasible because it is common for some chemical concentrations to be recorded as being below the analytical reporting limit. This creates special problems in the analysis of the data. A new model selection procedure, named forward censored regression, is introduced for selecting an appropriate model for environmental data with censored observations. The procedure is demonstrated using concentrations of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), deethylatrazine (DEA, 2-amino-4-chloro-6-isopropylamino-s-triazine), and deisopropylatrazine (DIA, 2-amino-4-chloro-6-ethylamino-s-triazine) in groundwater in the midwestern United States by using the data derived from a previous study conducted by the U.S. Geological Survey. More than 80% of the observations for each compound for this study were left censored at 0.05 mu g/L. The values for censored observations of atrazine, DEA, and DIA are imputed with the selected models. The summation of atrazine residue (atrazine + DEA + DIA) can then he calculated using the combination of observed and imputed values to generate a pseudo-complete data set. The all-subsets regression procedure is applied to the pseudo-complete data to select the final model for atrazine residue. The methodology presented can be used to analyze similar cases of environmental contamination involving censored data.