摘要:

This article investigates the consequences of departures from independence when the component lifetimes in a series system are exponentially distributed. Such departures are studied when the joint distribution is assumed to follow either one of the three Gumbel bivariate exponential models, the Downton bivariate exponential model, or the Oakes bivariate exponential model. Two distinct situations are considered. First, in theoretical modeling of series systems, when the distribution of the component lifetimes is assumed, one wishes to compute system reliability and mean system life. Second, errors in parametric and nonparametric estimation of component reliability and component mean life are studied based on life-test data collected on series systems when the assumption of independence is made

ISSN:0361-0918    

DOI:10.1080/03610918708812602

出版商:Marcel Dekker, Inc.    

年代:1987

数据来源: Taylor

摘要:

This paper is concerned with a fixed size subset selection problem for Bernoulli populations in the framework of the indifference zone approach. The goal is to select s populationswhich contain at least c of those with the t largest success probabilities. In order to control the probability of correct selection over the preference zone extensive tables of exact minimum sample sizes have been prepared to implement the single-stage procedure generalized from the well-known Sobel-Huyett procedure. It is shown how the tables can also be employed to design certain closedsequential procedures. These procedures curtail the sampling process of the single-stage procedureand may differ in their sampling rules. Two procedures working with play-the-winner rules are described in detail

ISSN:0361-0918    

DOI:10.1080/03610918708812603

出版商:Marcel Dekker, Inc.    

年代:1987

数据来源: Taylor

摘要:

Evidence presented by Fomby and Guilkey (1983) suggests that Hatanaka's estimator of the coefficients in the lagged dependent variable-serial correlation regression model performs poorly, not because of poor selection of the estimate of the autocorrelation coefficient, but because of the lack of a first observation correction. This study conducts a Monte Carlo investigationof the small sample efficiency gains obtainable from a first observation correction suggested by Harvey (1981). Results presented here indicate that substantial gains result from the first observation correction. However, in comparing Hatanaka's procedure with first observation correction to maximum likelihood search, it appears that ignoring the determinantal term of the full likelihood function causes some loss of small sample efficiency. Thus, when computer costsand programming constraints are not binding, maximum likelihood search is to be recommended. In contrast, users who have access to only rudimentary least squares programs would be well served when using Hatanaka's two-step procedure with first

ISSN:0361-0918    

DOI:10.1080/03610918708812604

出版商:Marcel Dekker, Inc.    

年代:1987

数据来源: Taylor

摘要:

The semi-variogram is widely used in geostatistical data analyses. It is estimatedby the sample semi-variogram. Although some theoretical work has been done on its sampling distribution for a Gaussian process these results are not of immediate practical usage because of the problems induced by the presence of spatial inter-correlations. In this paper various simulation studies are reported which give overwhelming evidence that a logarithmic transformation of the semi-variogram gives approximate normality for moderately large sample sizes. This result is theoretically expected under certain conditions. A robust estimator of the semi-variogram was also studied using the simulations.

ISSN:0361-0918    

DOI:10.1080/03610918708812605

出版商:Marcel Dekker, Inc.    

年代:1987

数据来源: Taylor