bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of failure time hierarchical data in the presence of competing risks with application to oral contraceptive pill use in Egypt
Authors: Ali Mohamed M. , Babiker Abdel G. , Cleland John G. 
Published: August 2002

AbstractProblems of practical interest in the analysis of data on contraceptive use, from Demographic and Health Surveys (DHS), include the estimation of the cause‐specific probability of discontinuation by timet(the cumulative incidence function), in the presence of other competing causes and the evaluation of the effect of covariates on the cause‐specific hazards of discontinuation. Methods of analysis of failure time data with competing risks are by now fairly well developed in the case of a simple random sample. However, the data from the DHS are clustered by geographical areas and include multiple episodes per woman. For a marginal (population average) approach, we propose using methods developed for simple random samples with standard errors calculated using a double bootstrap to take account of the clustered hierarchical nature of the data. In the conditional approach, the cause‐specific hazards are modelled as log‐linear functions of the covariates conditional on random effects of clusters and women, using a three‐level multinomial discrete‐time logit model. The methods are applied to data from Egypt 1992 DHS on the oral contraceptive pill use. Copyright © 2001 John Wiley & Sons, Ltd.
Sure outcomes of random events: a model for clinical trials
Authors: Bouckaert A. , Mouchart M. 
Published: August 2002

AbstractWe consider the outcomes of a clinical trial as determined by one, or several, possibly hidden causes. This paper proposes a statistical model that allows such a distinction of causes not only for the main, or therapeutic, effects but also for the side, or toxic, effects. More specifically, we focus on trials where the effects are naturally dichotomized, that is, where the health of a patient has improved or not, and where a specific adverse effect has occurred or not. A case study provides an example of the way this model can help to solve some problems of suspected drug toxicity. Finally, the model is shown to be a part of a hierarchy of models and the way to select a best model is investigated. Copyright © 2001 John Wiley & Sons, Ltd.
Modelling survival data with a cured fraction using frailty models
Authors: Price Dionne L. , Manatunga Amita K. 
Published: August 2002

AbstractCure models have historically been utilized to analyse time‐to‐event data with a cured fraction. We consider the use of frailty models as an alternative approach to modelling such data. An attractive feature of the models is the allowance for heterogeneity in risk among those individuals experiencing the event of interest in addition to the incorporation of a cured component. Utilizing maximum likelihood techniques, we fit models to data concerning the recurrence of leukaemia among patients receiving autologous transplantation treatment. The analysis suggests that the gamma frailty mixture model and the compound Poisson improve on the fit of the leukaemia data as compared to the standard cure model. Copyright © 2001 John Wiley & Sons, Ltd.
Testing for elevated disease rates using smoothed estimates
Authors: Downer Robert G. 
Published: August 2002

AbstractA method of testing for elevated disease rates using smoothed estimates is introduced for counts aggregated to a specific administrative level. A test statistic is developed based on an approximation to the smoothed estimate from a penalized multinomial likelihood and an approximate critical value is derived. Empirical investigation reveals that smoothing can increase the ability to detect elevated rates. The methods are applied to data on gastric cancer in Nova Scotia, Canada. Copyright © 2001 John Wiley & Sons, Ltd.
An alternative parameterization of the general linear mixture model for longitudinal data with non‐ignorable drop‐outs
Authors: Fitzmaurice Garrett M. , Laird Nan M. , Shneyer Lucy 
Published: August 2002

AbstractThis paper considers the mixture model methodology for handling non‐ignorable drop‐outs in longitudinal studies with continuous outcomes. Recently, Hogan and Laird have developed a mixture model for non‐ignorable drop‐outs which is a standard linear mixed effects model except that the parameters which characterize change over time depend also upon time of drop‐out. That is, the mean response is linear in time, other covariates and drop‐out time, and their interactions. One of the key attractions of the mixture modelling approach to drop‐outs is that it is relatively easy to explore the sensitivity of results to model specification. However, the main drawback of mixture models is that the parameters that are ordinarily of interest are not immediately available, but require marginalization of the distribution of outcome over drop‐out times. Furthermore, although a linear model is assumed for the conditional mean of the outcome vector given time of drop out, after marginalization, the unconditional mean of the outcome vector is not, in general, linear in the regression parameters. As a result, it is not possible to parsimoniously describe the effects of covariates on the marginal distribution of the outcome in terms of regression coefficients. The need to explicitly average over the distribution of the drop‐out times and the absence of regression coefficients that describe the effects of covariates on the outcome are two unappealing features of the mixture modelling approach. In this paper we describe a particular parameterization of the general linear mixture model that circumvents both of these problems. Copyright © 2001 John Wiley & Sons, Ltd.
Sample size re‐estimation: recent developments and practical considerations
Authors: Gould A. Lawrence 
Published: August 2002

AbstractInterim findings of a clinical trial often will be useful for increasing the sample size if necessary to provide the required power against the null hypothesis when the alternative hypothesis is true. Strategies for carrying out the interim examination that have been described over the past several years include ‘internal pilot studies’, blinded interim sample size adjustment and conditional power. Simulation studies show that the alternative methods generally control the type I error rate satisfactorily, although the power properties are more variable. The important issues associated with sample size re‐estimation are strategic, not numeric. Clearly expressed regulatory preferences suggest that methods not requiring unblinding the data before completion of the trial would be most appropriate. Extending a trial has its risks. The investigators/patients enrolled later in the course of a trial are not necessarily the same as those recruited/entered early. Re‐activating the enrolment process may be sufficiently complicated and expensive to justify enrolling more investigators/patients at the outset. Since sample size re‐estimation adjusts the sample size on the basis of variability while efficacy interim analysis adjusts the sample size based on the basis of estimated effect size, both principles can be used in the same trial. Sample size re‐estimation may not be advisable for trials involving extended follow‐up of individual patients or, more generally, when the follow‐up time is long relative to the recruitment time. In such cases, it may be better to estimate the sample size conservatively and introduce an interim efficacy evaluation. Copyright © 2001 John Wiley & Sons, Ltd.
Sample size recalculation using conditional power
Authors: Denne Jonathan S. 
Published: August 2002

AbstractThe sample size required to achieve a given power at a prespecified absolute difference in mean response may depend on one or more nuisance parameters, which are usually unknown. Proposed methods for using an internal pilot to recalculate the sample size using estimates of these parameters have been well studied. Most of these methods ignore the fact that data on the parameter of interest from within this internal pilot will contribute towards the value of the final test statistic. We propose a method which involves recalculating the target sample size by computing the number of further observations required to maintain the probability of rejecting the null hypothesis at the end of the study under the prespecified absolute difference in mean response conditional on the data observed so far. We do this within the framework of a two‐group error‐spending sequential test, modified so as to prevent inflation of the type I error rate. Copyright © 2001 John Wiley & Sons, Ltd.
Exact inference for categorical data: recent advances and continuing controversies
Authors: Agresti Alan 
Published: August 2002

AbstractMethods for exact small‐sample analyses with categorical data have been increasingly well developed in recent years. A variety of exact methods exist, primarily using the approach that eliminates unknown parameters by conditioning on their sufficient statistics. In addition, a variety of algorithms now exist for implementing the methods. This paper briefly summarizes the exact approaches and describes recent developments. Controversy continues about the appropriateness of some exact methods, primarily relating to their conservative nature because of discreteness. This issue is examined for two simple problems in which discreteness can be severe – interval estimation of a proportion and the odds ratio. In general, adjusted exact methods based on the mid‐P‐value seem a reasonable way of reducing the severity of this problem. Copyright © 2001 John Wiley & Sons, Ltd.
Zero‐inflated Poisson regression with random effects to evaluate an occupational injury prevention programme
Authors: Yau Kelvin K. W. , Lee Andy H. 
Published: August 2002

AbstractThis study presents a zero‐inflated Poisson regression model with random effects to evaluate a manual handling injury prevention strategy trialled within the cleaning services department of a 600 bed public hospital between 1992 and 1995. The hospital had been experiencing high annual rates of compensable injuries of which over 60 per cent were attributed to manual handling. The strategy employed Workplace Risk Assessment Teams (WRATS) that utilized a workplace risk identification, assessment and control approach to manual handling injury hazard reduction. The WRATS programme was an intervention trial, covering the 1988–1995 financial years. In the course of compiling injury counts, it was found that the data exhibited an excess of zeros, in the context that the majority of cleaners did not suffer any injuries. This phenomenon is typical of data encountered in the occupational health discipline. We propose a zero‐inflated random effects Poisson regression model to analyse such longitudinal count data with extra zeros. The WRATS intervention and other concomitant information on individual cleaners are considered as fixed effects in the model. The results provide statistical evidence showing the value of the WRATS programme. In addition, the methods can be applied to assess the effectiveness of intervention trials on populations at high risk of manual handling injury or indeed of injury from other hazards. Copyright © 2001 John Wiley & Sons, Ltd.
A general family of distributions for longitudinal dependence with special reference to event histories
Authors: Lindsey J. K. 
Published: August 2002

AbstractEvent histories play an increasingly important role in medical studies. Examples include times between recurrences of tumours, as with bladder cancer, and between repeated infections, as with chronic granulotomous disease. A general method for generating new distributions is proposed by introducing an intensity function into a density. This procedure yields, as special cases, several distributions already proposed in the literature. The families of distributions based on the Pareto distribution are of particular interest for event history analysis because of their relationship to the Laplace transform of a gamma distribution. They can yield multivariate distributions, with longitudinal (serial) dependence by a procedure similar to updating in the Kalman filter and with uniform dependence in a similar way to copulas. For longitudinal dependence, several such updating procedures are proposed. Copyright © 2001 John Wiley & Sons, Ltd.
On the inappropriateness of an EM algorithm based procedure for blinded sample size re‐estimation
Authors: Friede Tim , Kieser Meinhard 
Published: August 2002

AbstractWhen planning a clinical trial the sample size calculation is commonly based on ana prioriestimate of the variance of the outcome variable. Misspecification of the variance can have substantial impact on the power of the trial. It is therefore attractive to update the planning assumptions during the ongoing trial using an internal estimate of the variance. For this purpose, an EM algorithm based procedure for blinded variance estimation was proposed for normally distributed data. Various simulation studies suggest a number of appealing properties of this procedure. In contrast, we show that (i) the estimates provided by this procedure depend on the initialization, (ii) the stopping rule used is inadequate to guarantee that the algorithm converges against the maximum likelihood estimator, and (iii) the procedure corresponds to the special case of simple randomization which, however, in clinical trials is rarely applied. Further, we show that maximum likelihood estimation leads to no reasonable results for blinded sample size re‐estimation due to bias and high variability. The problem is illustrated by a clinical trial in asthma. Copyright © 2002 John Wiley & Sons, Ltd.
Motivation, cognitions and traits: predicting occupational health, well‐being and performance
Authors: Code Sharon , Langan‐Fox Janice 
Published: August 2002

AbstractPast research on vulnerability/resistance to occupational stress and strain has focused predominantly on personality defined at the trait or dispositional level (e.g. Type A Behaviour Pattern, Locus of Control, Dispositional Optimism and Negative Affectivity). This is problematic for two reasons. First, within the current, prevailing integrative view of personality there are three main elements: motivation, cognitions, and traits (Winter, 1996; McAdams, 2000). The second problem is that there are two branches that together define personality psychology as a discipline: (a) the nomothetic or ‘individual difference’ approach; and (b) the ‘ideographic’ approach, that is the structure and organization of personality at the individual level (Epstein, 1994), yet trait theory—and especially the ‘Big Five’ model—have paid little attention to the latter, a trend that is also evident in the occupational stress literature. The central thesis of the current paper is that motivation, cognitions and traits should contribute more variance to the stress–strain relationship than trait personality alone. A preliminary model is presented and recommendations for future research provided. Copyright © 2001 John Wiley & Sons, Ltd.
Alliance entrepreneurship and firm market performance
Authors: Sarkar MB , Echambadi RAJ , Harrison Jeffrey S. 
Published: August 2002

AbstractThis paper extends entrepreneurship into the domain of alliances, and investigates the effect of alliance proactiveness on market‐based firm performance (defined in terms of sales growth, market share, market development and product development). Alliance proactiveness is defined as the extent to which an organization engages in identifying and responding to partnering opportunities. The effect of alliance proactiveness on performance is tested within a contingency framework, with size and perceived environmental uncertainty as moderators, and using data from 182 firms. We estimated the model using partial least squares. Results indicate that alliance proactiveness leads to superior market‐based performance, and that this effect is stronger for small firms and in unstable market environments. Copyright © 2001 John Wiley & Sons, Ltd.
A resource‐based view of manufacturing strategy and the relationship to manufacturing performance
Authors: Schroeder Roger G. , Bates Kimberly A. , Junttila Mikko A. 
Published: August 2002

AbstractThis paper examines manufacturing strategy from the perspective of the resource‐based view of the firm. It explores the role of resources and capabilities in manufacturing plants that cannot be easily duplicated, and for which ready substitutes are not available. Such resources and capabilities are formed by employees' internal learning based on cross‐training and suggestion systems, external learning from customers and suppliers, and proprietary processes and equipment developed by the firm. Based on data from 164 manufacturing plants, the paper empirically demonstrates that competitive advantage in manufacturing (as measured by superior plant performance) results from proprietary processes and equipment which, in turn, is driven by external and internal learning. The implication is that resources such as standard equipment and employees with generic skills obtainable in factor markets are not as effective in achieving high levels of plant performance, since they are freely available to competitors. The paper also demonstrates the important role of internal and external learning in developing resources that are imperfectly imitable and difficult to duplicate. Copyright © 2002 John Wiley & Sons, Ltd.
An object‐oriented design for graph visualization
Authors: Marshall M. S. , Herman I. , Melançon G. 
Published: August 2002

AbstractMany applications, from everyday file system browsers to visual programming tools, require the display of network and graph structures. The Graph Visualization Framework (GVF) (available at http://www.cwi.nl/InfoVisu/GVF) is an architecture that supports the tasks common to most graph browsers and editors. This article gives a brief overview of the design of the GVF and focuses on the core classes that are used to represent and manipulate graphs. The design of the core classes is justified by the requirements for navigation and visualization. Copyright © 2001 John Wiley & Sons, Ltd.
Tool integration for flexible simulation of distributed algorithms
Authors: Khanvilkar Shashank , Shatz Sol M. 
Published: August 2002

AbstractOver the last two decades, considerable research has been done in distributed operating systems, which can be attributed to faster processors and better communication technologies. A distributed operating system requires distributed algorithms to provide basic operating system functionality likemutual exclusion,deadlock detection, etc. A number of such algorithms have been proposed in the literature. Traditionally, these distributed algorithms have been presented in a theoretical way, with limited attempts to simulate actual working models. This paper discusses our experience in simulating distributed algorithms with the aid of some existing tools, including OPNET and Xplot. We discuss our efforts to define a basic model‐based framework for rapid simulation and visualization, and illustrate how we used this framework to evaluate some classic algorithms. We have also shown how the performance of different algorithms can be compared based on some collected statistics. To keep the focus of this paper on the approach itself, and our experience with tool integration, we only discuss some relatively simple models. Yet, the approach can be applied to more complex algorithm specifications. Copyright © 2001 John Wiley & Sons, Ltd.
We enter the twenty‐first century with schooling designed in the nineteenth
Authors: Banathy Bela H. 
Published: August 2002

AbstractRecognizing that the current system of schooling is grounded in – and was designed for – the industrial machine age of the nineteenth century, this paper brings into focus the necessity of designing new systems of learning and human development that are in‐sync with the new realities of the information/knowledge age and are capable to co‐evolve with the emerging society of the new century. The paper offers an approach to the design and self‐organization of these new systems. In closing, two educational images are projected; one stands for ‘the new story of education’, the other depicts ‘the old story.’ Copyright © 2001 John Wiley & Sons, Ltd.
Non‐trivial solutions to theN‐person Prisoners' Dilemma
Authors: Szilagyi Miklos N. , Szilagyi Zoltan C. 
Published: August 2002

AbstractWe have developed a new agent‐based simulation tool to model social dilemmas for the case of a large number of not necessarily rational decision‐makers (Szilagyi and Szilagyi,2000). The combination of various personalities with stochastic learning makes it possible to simulate the multi‐person Prisoners' Dilemma game for realistic situations. A variety of personality profiles and their arbitrary combinations can be represented, including agents whose probability of cooperation changes by an amount proportional to its reward from the environment. For the case of such agents the game has non‐trivial but remarkably regular solutions. We discuss a method and present an algorithm for making accurate advance predictions of these solutions. We also propose our model as a viable approach for the study of populations of cells, organisms, groups, organizations, communities, and societies. It may lead to better understanding of the evolution of cooperation in living organisms, international alliances, sports teams, and large organizations. Copyright © 2002 John Wiley & Sons, Ltd.
Lateral ligament: Its anatomy and clinical importance
Authors: Takahashi Takashi , Ueno Masashi , Azekura Kaoru , Ohta Hirotoshi 
Published: August 2002

AbstractSince Miles proposed abdominoperineal excision as a radical surgery for rectal cancer in 1908, surgeons have recognized the lateral ligament in the pararectal space of their patients and attached clinical importance to it, although anatomists did not describe any such configuration in cadavers. By analyzing an experience of 421 lower rectal cancer cases at the Cancer Institute Hospital in Tokyo, discussion of the lateral ligament was focused on its relationship to the fascial arrangements in the pelvis, the pelvic autonomic nervous system, and the lymphatic drainage of the rectum. The lateral ligament is not an anatomical term, but a clinical or surgical one. It exists in a living pelvis as a condensation of connective tissue around the middle rectal artery and is divided into two segments by the inferior hypogastric nerve plexus inside it and the visceral endopelvic fascia around it. The lateral ligament is a pathway of blood vessels and nerve fibers toward the rectum and lymphatic vessels from the lower rectum toward the iliac lymph nodes. Therefore, the lateral ligament plays a critical role in surgery for lower rectal cancer in two respects: the anatomic extent of resection for curing rectal cancer, and the preservation of sexual function. Semin. Surg. Oncol. 19:386–395, 2000. © 2000 Wiley‐Liss, Inc.