摘要:

AbstractA practical approach is proposed for model selection and discrimination among nested and non‐nested probability distributions. Some existing problems with traditional model selection approaches are addressed, including standard testing of a null hypothesis against a more general alternative and the use of some well‐known discrimination criteria for non‐nested distributions. A generalized information criterion (GIC) is used to choose from two or more model structures or probability distributions. For each set of random samples, all model structures that do not perform significantly worse than other candidates are selected. The two‐and three‐parameter gamma, Weibull and lognormal distributions are used to compare the discrimination procedures with traditional approaches. Monte Carlo experiments are employed to examine the performances of the criteria and tests over large sets of finite samples. For each distribution, the Monte Carlo procedure is undertaken for various representative sets of parameter values which are encountered in fitting environmental qua

ISSN:1180-4009    

DOI:10.1002/env.3170010301

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper presents a stochastic procedure for the solution of groundwater flow through a random shallow semiconfined aquifer. Problems dealing with flow through a semiconfined aquifer with multiple random parameters subject to deterministic boundary conditions and domain recharge are investigated using perturbation techniques associated with boundary element methods. Both the transmissivity of the main aquifer and the resistance of the leaky layer are considered as random parameters. The perturbation boundary element method does not require specification of the probability density function of the parameters but only their expectations, variances and the covariance of the two parameters. To illustrate the applicability of the method, three simple numerical examples are presented. A one‐dimensional example is examined and compared with the exact solution, along with the perturbation solutions for two two‐dimensional flow probl

ISSN:1180-4009    

DOI:10.1002/env.3170010302

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractIn routine water quality monitoring of toxic contaminants, a number of difficulties are usually encountered in the statistical interpretation of the results. A major reason for this is the frequent occurrence of water sample concentrations below the limit of detection. In this paper the issue of dealing with values below the detection limit is discussed through a case study using data from the South Saskatchewan River. Some comments are also given outlining the properties and the difficulties associated with the commonly used ad hoc methods for estimating the population characteristics when the data are subject to type I censoring. Specifically inferences about the mean value, trend and seasonal changes are considered.

ISSN:1180-4009    

DOI:10.1002/env.3170010303

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA preliminary test estimator is a method of combining information from two experiments in a problem of estimating a parameter. The asymptotics of this estimator in the case of estimating a population mean is considered in a setting of a local alternative. Asymptotic confidence intervals are obtained using the asymptotic distribution.

ISSN:1180-4009    

DOI:10.1002/env.3170010304

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY