Nonparametric Bootstrap Method for Estimation Upper Confidence Limits for Exposure Point Concentration of Formaldehyde in Fur Products - A Case Study of Tongxiang City, China

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Xuzheng Yuan
Xuechaun Wang
Weina Lu
Sujie Jiang


The distribution characteristics of the formaldehyde (FA)content of fur products produced in Tongxiang City over threeconsecutive years (2014-2016) were analyzed by the Lillieforstest, quarterback robust statistical method, and kernel densityestimation. The bootstrap simulation sampling method wasused to calculate the upper confidence limits (UCL) of theexposure point concentration (EPC) of FA. The robustness andrationality of the UCL estimation were verified by thedistribution of the mean value of each bootstrap sample dataset.The results showed that their distributions were close to normaldistribution but were highly skewed. The one-sided 95% UCL onthe mean were 95.45 mg/kg, 93.02 mg/kg and 86.64 mg/kg,which decreased year by year. The Wilcoxon rank sum testindicated that the population distribution of the FA content in2016 showed a structural improvement over those of the previoustwo years.

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