Statistical Evaluation of the Influence of Flow Conditions and Sampling Techniques on Water Quality Data
Authors: Daas, Mutaz; Srivastava, Rajiv; Conklin, Walter
Source: Water Environment Research, Volume 79, Number 2, February 2007 , pp. 147-155(9)
Publisher: Water Environment Federation
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Abstract:
The purpose of this study is to statistically evaluate the influence of various sampling methodologies and flow conditions on the quality and comparability of total phosphorus concentration data collected over the course of 27 months at the South Florida Water Management District (SFWMD) S-65E structure. The data was obtained from the following sampling methodologies: U.S. Geological Survey (USGS) (Reston, Virginia) equal width increment spatially composite grab samples, USGS replicate samples, SFWMD grab samples, and SFWMD autosampler samples. Both significant and insignificant differences were reported from these comparisons. Parametric and nonparametric standard statistical tests for significance were carried out to evaluate the differences between the data. To avoid invalid conclusions of insignificant differences, we conducted tests for equivalence of the means and variances. The results from the data analysis revealed that both flow conditions and sampling methodology affected the water quality data.Keywords: total phosphorus; natural streams; free surface; flow conditions; representative; sampling; water quality; t-test; Wilcoxon rank sum test; equivalence; variance
Document Type: Research article
DOI: 10.2175/106143006X102051
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