Inferences about the mean from censored water quality data / by A.H. El-Shaarawi. : En13-5/87-141E-PDF

"Several methods which are commonly used for making inferences about the levels of many metals and organic contaminants in ambient waters from type I censored data are critically evaluated and their applications are illustrated using the concentrations of PCB in water samples from the Niagara River. Difficulties encountered in the application of all the methods, except the method of maximum likelihood, include the occurrence of inadmissible estimates for the censored values and the unavailability of the standard errors for these estimates. Under the assumption that the distribution of the data is lognormal, the log regression method is modified to produce admissible estimates of the censored values and the properties of the maximum likelihood estimates for the lognormal mean are derived. Furthermore, an approximate confidence interval for the lognormal mean is given and its use for estimating the load to and from the Niagara River is illustrated"--Abstract.

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publications.gc.ca/pub?id=9.870432&sl=1

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