Insider Censoring: Distortion of Data with Nondetects
| Autor: | Dennis R. Helsel |
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| Rok vydání: | 2005 |
| Předmět: | |
| Zdroj: | Human and Ecological Risk Assessment: An International Journal. 11:1127-1137 |
| ISSN: | 1549-7860 1080-7039 |
| Popis: | Environmental data often include low-level concentrations below reporting limits. These data may be reported as “< RL,” where RL is one of several types of reporting limits. Some values also may be reported as a single number, but flagged with a qualifier (J-values) to indicate a difference in precision as compared to values above the RL. A currently used method for reporting censored environmental data called “insider censoring” produces a strong upward bias, while also distorting the shape of the data distribution. This results in inaccurate estimates of summary statistics and regression coefficients, distorts evaluations of whether data follow a normal distribution, and introduces inaccuracies into risk assessments and models. Insider censoring occurs when data measured as below the detection limit (< DL) are reported as less than the higher quantitation limit (< QL), whereas values between the DL and QL are reported as individual numbers. Three unbiased alternatives to insider censoring are p... |
| Databáze: | OpenAIRE |
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