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EVALUTING STREAM STANDARD VIOLATIONS USING A WATER QUALITY DATA BASE 1
Author(s) -
Loftis Jim C.,
Ward Robert C.
Publication year - 1981
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.1981.tb01945.x
Subject(s) - statistics , nonparametric statistics , confidence interval , point estimation , sampling (signal processing) , sample (material) , quality (philosophy) , mathematics , standard deviation , water quality , computer science , ecology , philosophy , chemistry , filter (signal processing) , chromatography , epistemology , computer vision , biology
Cumulative density functions (c.d.f.'s) for water quality random variables may be estimated using data from a routine grab sampling program. The c.d.f. may then be used to estimate the probability that a single grab sample will violate a given stream standard and to determine the anticipated number of violations in a given number of samples. Confidence limits about a particular point on the c.d.f. may be used to reflect the accuracy with which the sample estimate represents the true c.d.f. Methods are presented here for calculating such confidence limits using both a normal model and a nonparametric model. Examples are presented to illustrate the usefulness of an estimated c.d.f. and associated confidence limits in assessing whether an observed number of standard violations is the result of natural variability or represents real degradation in water quality.