bluuebunny/crossref_metadata_2025_split huggingface dataset:
Missing Covariates in Generalized Linear Models When the Missing Data Mechanism is Non-ignorable
Authors: Ibrahim Joseph G. , Lipsitz Stuart R. , Chen Ming-Hui 
Published: March 2003

Summary
We propose a method for estimating parameters in generalized linear models with missing covariates and a non-ignorable missing data mechanism. We use a multinomial model for the missing data indicators and propose a joint distribution for them which can be written as a sequence of one-dimensional conditional distributions, with each one-dimensional conditional distribution consisting of a logistic regression. We allow the covariates to be either categorical or continuous. The joint covariate distribution is also modelled via a sequence of one-dimensional conditional distributions, and the response variable is assumed to be completely observed. We derive the E- and M-steps of the EM algorithm with non-ignorable missing covariate data. For categorical covariates, we derive a closed form expression for the E- and M-steps of the EM algorithm for obtaining the maximum likelihood estimates (MLEs). For continuous covariates, we use a Monte Carlo version of the EM algorithm to obtain the MLEs via the Gibbs sampler. Computational techniques for Gibbs sampling are proposed and implemented. The parametric form of the assumed missing data mechanism itself is not ‘testable' from the data, and thus the non-ignorable modelling considered here can be viewed as a sensitivity analysis concerning a more complicated model. Therefore, although a model may have ‘passed' the tests for a certain missing data mechanism, this does not mean that we have captured, even approximately, the correct missing data mechanism. Hence, model checking for the missing data mechanism and sensitivity analyses play an important role in this problem and are discussed in detail. Several simulations are given to demonstrate the methodology. In addition, a real data set from a melanoma cancer clinical trial is presented to illustrate the methods proposed.
Generalized Spectral Tests for Serial Dependence
Authors: Hong Yongmiao 
Published: March 2003

Summary
Two tests for serial dependence are proposed using a generalized spectral theory in combination with the empirical distribution function. The tests are generalizations of the Cramér-von Mises and Kolmogorov-Smirnov tests based on the standardized spectral distribution function. They do not involve the choice of a lag order, and they are consistent against all types of pairwise serial dependence, including those with zero autocorrelation. They also require no moment condition and are distribution free under serial independence. A simulation study compares the finite sample performances of the new tests and some closely related tests. The asymptotic distribution theory works well in finite samples. The generalized Cramér-von Mises test has good power against a variety of dependent alternatives and dominates the generalized Kolmogorov-Smirnov test. A local power analysis explains some important stylized facts on the power of the tests based on the empirical distribution function.
Dealing With Label Switching in Mixture Models
Authors: Stephens Matthew 
Published: March 2003

Summary
In a Bayesian analysis of finite mixture models, parameter estimation and clustering are sometimes less straightforward than might be expected. In particular, the common practice of estimating parameters by their posterior mean, and summarizing joint posterior distributions by marginal distributions, often leads to nonsensical answers. This is due to the so-called ‘label switching’ problem, which is caused by symmetry in the likelihood of the model parameters. A frequent response to this problem is to remove the symmetry by using artificial identifiability constraints. We demonstrate that this fails in general to solve the problem, and we describe an alternative class of approaches, relabelling algorithms, which arise from attempting to minimize the posterior expected loss under a class of loss functions. We describe in detail one particularly simple and general relabelling algorithm and illustrate its success in dealing with the label switching problem on two examples.
Following a Moving Target—Monte Carlo Inference for Dynamic Bayesian Models
Authors: Gilks Walter R. , Berzuini Carlo 
Published: March 2003

Summary
Markov chain Monte Carlo (MCMC) sampling is a numerically intensive simulation technique which has greatly improved the practicality of Bayesian inference and prediction. However, MCMC sampling is too slow to be of practical use in problems involving a large number of posterior (target) distributions, as in dynamic modelling and predictive model selection. Alternative simulation techniques for tracking moving target distributions, known as particle filters, which combine importance sampling, importance resampling and MCMC sampling, tend to suffer from a progressive degeneration as the target sequence evolves. We propose a new technique, based on these same simulation methodologies, which does not suffer from this progressive degeneration.
A Measure of Disclosure Risk for Microdata
Authors: Skinner C. J. , Elliot M. J. 
Published: March 2003

SummaryProtection against disclosure is important for statistical agencies releasing microdata files from sample surveys. Simple measures of disclosure risk can provide useful evidence to support decisions about release. We propose a new measure of disclosure risk: the probability that a unique match between a microdata record and a population unit is correct. We argue that this measure has at least two advantages. First, we suggest that it may be a more realistic measure of risk than two measures that are currently used with census data. Second, we show that consistent inference (in a specified sense) may be made about this measure from sample data without strong modelling assumptions. This is a surprising finding, in its contrast with the properties of the two ‘similar’ established measures. As a result, this measure has potentially useful applications to sample surveys. In addition to obtaining a simple consistent predictor of the measure, we propose a simple variance estimator and show that it is consistent. We also consider the extension of inference to allow for certain complex sampling schemes. We present a numerical study based on 1991 census data for about 450 000 enumerated individuals in one area of Great Britain. We show that the theoretical results on the properties of the point predictor of the measure of risk and its variance estimator hold to a good approximation for these data.
Bovine Spongiform Encephalopathy Maternal Cohort Study—Exploratory Analysis
Authors: Gore Sheila M. , Gilks Walter R. , Wilesmith John W. 
Published: March 2003

SUMMARY
The bovine spongiform encephalopathy (BSE) maternal cohort study supports a role both for direct maternal transmission and for inherited genetic susceptibilty to the BSE agent. Additional data from the main BSE database do not resolve whether the risk of direct maternal transmission of BSE from dam to calf is concentrated in the interval within 5 months before the onset of BSE in the dam, as data from the BSE maternal cohort study suggest. The reason for this is that we cannot rely, as our analysis requires, on the survival of calves or traceability of the dam being independent of the interval from the birth of a calf to onset of BSE in the dam. Accordingly, for the present, we place most weight on evidence from the BSE maternal cohort study. Direct maternal transmission of the BSE agent from dam to calf has not been ruled out; vertical transmission of the new variant Creutzfeldt–Jakob disease (NVCJD) from mother with NVCJD to baby is therefore also possible. Actions to quantify, and minimize, the transmission risk, if any, from a mother with NVCJD to her baby, or to delivery teams, should be taken without delay.
Analysis of the Bovine Spongiform Encephalopathy Maternal Cohort Study: The Discordant Case–Control Pairs
Authors: Curnow R. N. , Hodge A. , Wilesmith J. W. 
Published: March 2003

SUMMARY
The progeny of the affected and non-affected dams in the bovine spongiform encephalopathy (BSE) cohort study were paired in terms of their farm of origin and approximate date of birth. This paper presents an exact logistic regression analysis that avoids modelling the differences between the pairs and so analyses only the discordant pairs. There is some evidence that the pairs in which the affected animal was born to the affected dam tend to be those in which the onset of BSE in the affected dam preceded or occurred soon after the calving. This suggests some occurrence of maternal transmission.
Software Reliability Assessment using Accelerated Testing Methods
Authors: Ehrlich Willa K. , Nair Vijayan N. , Alam M. S. , Chen W. H. , Engel Mark 
Published: March 2003

SUMMARY
The use of operational profiles and usage-based testing has received considerable attention recently in the software engineering literature. Testing under the actual operational profile can, however, be expensive, time consuming or even infeasible in situations where the performance of a system is dominated by infrequent but highly critical events. We consider a real application that deals with telecommunications network restoration after network failure caused by cuts in fibre optic cables. We use this application to demonstrate the usefulness of traditional accelerated testing methods to test and estimate software reliability. These methods, which have been extensively used in hardware reliability, have an important role to play in software reliability assessment as well.
Using Quantile Plots of the Prediction Variance for Comparing Designs for a Constrained Mixture Region: An Application Involving a Fertilizer Experiment
Authors: Khuri André I. , Harrison Jay M. , Cornell John A. 
Published: March 2003

SUMMARY
Summary. Vining and co-workers have used plots of the prediction variance trace (PVT) along the so-called prediction rays to compare mixture designs in a constrained region R. In the present paper, we propose a method for describing the distribution of the prediction variance within the region R by using quantile plots. More comprehensive comparisons between mixture designs are possible through the proposed plots than with the PVT plots. The utility of the quantile plots is illustrated with a four-component fertilizer experiment that was initiated in São Paulo, Brazil.
Proportional Hazards Models: A Latent Competing Risk Approach
Authors: Gelfand Alan E. , Ghosh Sujit K. , Christiansen Cindy , Soumerai Stephen B. , McLaughlin Thomas J. 
Published: March 2003

SUMMARY
We propose a novel semiparametric version of the widely used proportional hazards survival model. Features include an arbitrarily rich class of continuous base-line hazards, an attractive epidemiological interpretation of the hazard as a latent competing risk model and trivial handling of censoring. Models are fitted by using a data augmentation scheme. The methodology is applied to a data set recording times to first hospitalization following clinical diagnosis of acquired immune deficiency syndrome for a sample of 169 patients.
Anisotropic Spatial Sampling Designs for Urban Pollution
Authors: Arbia Giuseppe , Lafratta Giovanni 
Published: March 2003

SUMMARYIsotropic processes form an inadequate basis in modelling many spatially distributed data. In particular environmental phenomena often have strong anisotropic spatial variation, especially when the regions monitored are very large. We extend a recently proposed optimal sampling strategy by assuming a spatial anisotropic random field as the basis for the data generator mechanism. The procedure is based on a geographical space transformation indicated by Sampson and Guttorp. We discuss the optimal design and we develop a sequential procedure for selecting a network of monitoring stations in environmental surveys. Some data on sulphur dioxide pollution in Padua (Italy) are analysed to illustrate the method.
A Mixture Model to Assess The Effect of Hormonal Stimulation on the Development of Follicles in Prepubertal Heifers
Authors: Lambert Philippe 
Published: March 2003

SummaryThe goal of this study is to assess the effect of follicle stimulating hormone (FSH) on the growth of follicles in prepubertal heifers. Adams and co-workers have shown that follicles develop in waves as in post-pubertal heifers: after a few days, a dominant follicle arises on one of the two ovaries whereas the other subordinate follicles regress. The dominant follicle remains detectable when the next wave occurs. The number and the diameters of these follicles have been measured for 14 days. The same experiment was repeated after a 3-day FSH stimulation. Several large follicles now arise simultaneously on both ovaries together with small follicles which cannot be detected any more when the next wave occurs. Unfortunately, follicles were not individually tracked. Therefore a three-component mixture model was used to describe the potential simultaneous observation of dominant, decaying dominant and subordinate follicles before the FSH stimulation; the same type of model was considered for large, decaying large and small follicles after the hormonal stimulation. Moreover, for technical reasons, only follicles larger than 2 mm are observable. Measurements were thus left truncated. The models fitted are used to quantify the effects of the stimulation and to determine the ideal time point at which follicles should be punctured under ultrasonography to harvest ovocytes that will be fertilized and cultured in vitro.
Lee–Carter Mortality Forecasting: A Parallel Generalized Linear Modelling Approach for England and Wales Mortality Projections
Authors: Renshaw Arthur , Haberman Steven 
Published: March 2003

SummaryThe paper presents a reinterpretation of the model underpinning the Lee–Carter methodology for forecasting mortality (and other vital) rates. A parallel methodology based on generalized linear modelling is introduced. The use of residual plots is proposed for both methods to aid the assessment of the goodness of fit. The two methods are compared in terms of structure and assumptions. They are then compared through an analysis of the gender- and age-specific mortality rates for England and Wales over the period 1950–1998 and through a consideration of the forecasts generated by the two methods. The paper also compares different approaches to the forecasting of life expectancy and considers the effectiveness of the Coale–Guo method for extrapolating mortality rates to the oldest ages.
The Management of Redundancies in Europe: The Case of Great Britain
Authors: Deakin Simon , Wilkinson Frank 
Published: March 2003

The paper presents the findings of a comparative and interdisciplinary legal and economic study on managing labour redundancies in seven EU member countries. It is structured for immediate comparability between the systems examined. The introductory section contains an account of the evolution of the British labour market, with special reference to redundancy trends, the features of the programmes for managing redundancies, the roles of firms and the ‘external environment’ in handling workforce adjustments. The second section presents a map of policies that work to prevent labour redundancies (preventive measures) such as flexibility, training etc. Next, the instruments for handling temporary labour redundancies (retentive measures) are examined (e.g. short‐time working, temporary layoffs etc.). The following section is devoted to instruments and programmes involved in the management of permanent labour redundancies (expulsive measures), e.g. collective dismissals, severance pay etc. The final section provides an overall assessment of the British system for managing labour redundancies, and briefly discusses the national debate on the prospects for reform, in light of the principles and policies of convergence set forth by the European Union.
Doctors in a Wired World: Can Professionalism Survive Connectivity?
Authors: Blumenthal David 
Published: March 2003

The Information Revolution Has Raised Myriad questions about how the health care system will function in the future (Gingrich and Magaziner 2000; National Research Council 2000). The consensus seems to be that new information technologies will significantly affect almost every aspect of health care, from the way that employers and individuals purchase health insurance to the way that doctors and patients provide and receive care (National Research Council 2000).Although peer‐reviewed evidence to support these predictions is scarce, the available data suggest that the major health care actors are actively experimenting with the new capabilities to exchange information. A February 2002 survey by Harris Interactive (www.Harrisinteractive.com) found that 137 million Americans were users of the Internet and the World Wide Web and 110 million reported going on‐line at least three times a month to look for health care information (Landro 2002). An earlier survey by the Pew Charitable Trusts reported that of those Americans who used the Internet for health care purposes, 92 percent found the information useful.The information revolution has the potential to reduce the asymmetry of information between patients and doctors and thereby to undermine a central pillar of physicians' claim to professional status: the possession of distinctive competence based on technical know‐how selflessly applied and collectively monitored. A close analysis of the information revolution's likely effects suggests that for some patients with some conditions, their access to more and better information will indeed reduce the magic, mystery, and power of the medical profession. However, the information revolution also offers opportunities for physicians to bolster the cognitive and moral bases of professionalism. To seize those opportunities, physicians must master new roles and skills and avoid unacceptable conflicts of interest.
Navigating the Disability Process: Persons with Mental Disorders Applying for and Receiving Disability Benefits
Authors: Bilder Scott , Mechanic David 
Published: March 2003

The Social Security Disability benefit programs (SSDI and SSI) constitute an essential safety net for individuals unable to work because of disability. Eligibility for SSDI is based on work history and is viewed as an entitlement for individuals who meet disability criteria. SSI eligibility, however, depends on means testing and, although it is administered as a Social Security program, is seen more as income support for persons with disabilities who have not worked and cannot work. Ideally, such programs seek to provide assistance to those who most need it without encouraging those who can work to leave the workforce or to stop looking for work. The search for balance among meeting need, encouraging work, and containing public expenditures is a source of underlying tension that typifies such safety net programs. Outcomes depend on both the administration of the eligibility process and the processes by which persons and their associates become aware of the disability program, decide to apply, negotiate the application process, and succeed or fail in their attempts.Persons with mental disorders are less likely to be working and more likely to apply for and receive SSDI and/or SSI benefits than are those without such disorders. Data from the National Health Interview Survey on Disability (NHIS‐D) were examined to identify the predictors of SSDI/SSI application and receipt among persons with self‐reported mental disorders. Compared with nonapplicants, applicants had higher levels of disability, fewer financial and interpersonal resources, and better access to information about the disability programs. Among applicants, similar factors distinguished recipients from those who did not receive benefits. Navigating the disability process is associated with the extent of impairment, economic and social disadvantage, and linkage to the disability determination process.
Before demand‐side management is discarded, let’s see what pieces should be kept
Authors: Gellings Clark W. 
Published: March 2003

Over the last 15 years, demand‐side management (DSM) in developed countries has been transformed from a start‐up activity to a full‐blown industry, and then down‐sized to a modest activity. While DSM remains a part of some utilities' strategies to meet current and future customer needs, its image in developed countries has been tarnished and its future is in doubt.More than ever now, retail energy customers are demanding from the marketplace a broad range of energy products and services that satisfy their most important needs.The electric utility industry has evolved into an energy and energy services industry. Its strategies, of retaining customers, enhancing revenue and controlling costs through various programmes and initiatives, while meeting customer needs, do not necessarily include DSM; but, nor is DSM in conflict with them. It is now, therefore, time to move on from DSM in the developed world.However, in developing countries, where the growth in electric energy production and delivery systems has not kept pace with population, DSM remains a viable option.
Exchange Rates, Non‐Traded Goods and the Terms Of Trade: An Empirical Application for New Zealand
Authors: Hansen Eric , Hutchison Michael M. 
Published: March 2003

This article formulates and tests for New Zealand a model of exchange rate determination focusing on non‐tradeable goods and terms‐of‐trade shifts. We emphasize the equilibrium properties of this framework and, in this context, estimate an error correction model where adjustment in response to deviation from equilibrium is an important determinant of short‐run exchange rate movements.We estimate the model using a new data series on the supply of non‐tradeable goods. The model has desirable empirical characteristics, including a plausible error correction equation, strong support for cointegration and rapid convergence to the long‐run equilibrium. Moreover, a variety of diagnostic statistics, including parameter stability tests andout‐of‐sample forecasting performance, indicate the equation is a parsimonious representation of the data. These results provide considerable support for the emphasis on ‘real’ determinants of nominal exchange rates, in this case fluctuations in non‐traded goods supply and terms‐of‐trade.
Forestalling War in Kosovo: Opportunities Missed
Authors: Satterwhite James 
Published: March 2003

From the end of the 1980s until the late 1990s the main form of response on the part of the Kosovar Albanians to the Serbian repression initiated by Miloševíc was a campaign of nonviolent resistance.This campaign ultimately gave way to a more violent form of resistance when the Albanians became disillusioned by its lack of success, which in turn provoked a more violent Serbian response. This article assesses whether concrete initiatives by international organizations in the period from 1989 to 1999 could have helped support the nonviolent resistance to Serb repression and concludes that there were many ways in which more international support for this strategy could have helped avert the war in 1999 by strengthening nonviolent options.
Oliver Cromwell and a 1647 Case in Chancery
Authors: Farr David 
Published: March 2003

Abstract
The article considers aspects of Cromwell's finances, his relationship with John Thurloe and the marriage negotiations concerning his son Richard, all in the period 1646‐8. This is based on a previously unnoticed document from chancery proceedings in the Public Record Office. The article argues that Thurloe had a professional relationship with Cromwell earlier than previously thought. It sheds light on the marriage negotiations of Richard Cromwell and Dorothy Maijor and in particular on the transitional phase in Cromwell's finances.