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Impact of Outliers on the Statistical Measures of the Environmental Monitoring Data in Busan Coastal Sea
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  • Journal title : Ocean and Polar Research
  • Volume 38, Issue 2,  2016, pp.149-159
  • Publisher : Korea Institute of Ocean Science & Technology
  • DOI : 10.4217/OPR.2016.38.2.149
 Title & Authors
Impact of Outliers on the Statistical Measures of the Environmental Monitoring Data in Busan Coastal Sea
Cho, Hong-Yeon; Lee, Ki-Seop; Ahn, Soon-Mo;
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The statistical measures of the coastal environmental data are used in a variety of statistical inferences, hypothesis tests, and data-driven modeling. If the measures are biased, then the statistical estimations and models may also be biased and this potential for bias is great when data contain some outliers defined as extraordinary large or small data values. This study aims to suggest more robust statistical measures as alternatives to more commonly used measures and to assess the performance these robust measures through a quantitative evaluation of more typical measures, such as in terms of locations, spreads, and shapes, with regard to environmental monitoring data in the Busan coastal sea. The detection of outliers within the data was carried out on the basis of Rosner`s test. About 5-10% of the nutrient data were found to contain outliers based on Rosner`s test. After removal (zero-weighting) of the outliers in the data sets, the relative change ratios of the mean and standard deviation between before and after outlier-removal conditions revealed the figures 13 and 33%, respectively. The variation magnitudes of skewness and kurtosis are 1.36 and 8.11 in a decreasing trend, respectively. On the other hand, the change ratios for more robust measures regarding the mean and standard deviation are 3.7-10.5%, and the variation magnitudes of robust skewness and kurtosis are about only 2-4% of the magnitude of the non-robust measures. The robust measures can be regarded as outlier-resistant statistical measures based on the relatively small changes in the scenarios before and after outlier removal conditions.
statistical measures;robust measures;outlier;Rosner`s test;Busan coastal sea;
 Cited by
Distribution and Trend Analysis of the Significant Wave Heights Using KMA and ECMWF Data Sets in the Coastal Seas, Korea, Journal of Korean Society of Coastal and Ocean Engineers, 2017, 29, 3, 129  crossref(new windwow)
국가해양환경정보통합시스템 (2016) 해양환경측정망 원본자료. Accessed 18 Jan 2016 (Marine Environment Information System (2016) Raw data - marine environmental monitoring network. Accessed 18 Jan 2016)

해양환경관리공단 (2015) 국가해양환경측정망 자료 - 부산연안. Accessed 18 Jan 2016 (Korea Marine Environment Management Corporation (2016) National marine environmental monitoring network data - Busan coastal sea Accessed 18 Jan 2016)

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