bluuebunny/crossref_metadata_2025_split huggingface dataset:
A multiple imputation strategy for incomplete longitudinal data
Authors: Landrum Mary Beth , Becker Mark P. 
Published: August 2002

AbstractLongitudinal studies are commonly used to study processes of change. Because data are collected over time, missing data are pervasive in longitudinal studies, and complete ascertainment of all variables is rare. In this paper a new imputation strategy for completing longitudinal data sets is proposed. The proposed methodology makes use of shrinkage estimators for pooling information across geographic entities, and of model averaging for pooling predictions across different statistical models. Bayes factors are used to compute weights (probabilities) for a set of models considered to be reasonable for at least some of the units for which imputations must be produced, imputations are produced by draws from the predictive distributions of the missing data, and multiple imputations are used to better reflect selected sources of uncertainty in the imputation process. The imputation strategy is developed within the context of an application to completing incomplete longitudinal variables in the so‐called Area Resource File. The proposed procedure is compared with several other imputation procedures in terms of inferences derived with the imputations, and the proposed methodology is demonstrated to provide valid estimates of model parameters when the completed data are analysed. Extensions to other missing data problems in longitudinal studies are straightforward so long as the missing data mechanism can be assumed to be ignorable. Copyright © 2001 John Wiley & Sons, Ltd.
Bayesian model selection: analysis of a survival model with a surviving fraction
Authors: Seltman Howard , Greenhouse Joel , Wasserman Larry 
Published: August 2002

AbstractWe describe a methodology for model comparison in a Bayesian framework as applied to survival with a surviving fraction. This is illustrated using a case study of a randomized and controlled clinical trial investigating time until recurrence of depression. Posterior distributions are simulated using Metropolis‐within‐Gibbs Markov chain methods. Models reflecting the effects of covariates on the log odds of being in the surviving fraction, the log of the hazard rate, as well as both and neither are compared. Bayes factors for comparing the models are obtained by using the bridge sampling method of calculating normalizing constants. Copyright © 2001 John Wiley & Sons, Ltd.
Relative risk estimation and inference using a generalized logrank statistic
Authors: Mehrotra Devan V. , Roth Arthur J. 
Published: August 2002

AbstractWhen comparing two survival distributions with proportional hazard functions, the logrank test is optimal for testing the null hypothesis that the constant hazard ratio (relative risk) is one. In this paper, we focus on (i) testing for departures from a relative risk other than one, and (ii) estimation of the relative risk. The standard tool to address both (i) and (ii) is the Cox proportional hazards model. However, the performance of the Cox model can be less than optimal with small samples. We show why this is the case, and propose a simple alternative method of estimation and inference based on a generalized logrank (GLR) statistic. While the GLR and Cox model approaches are asymptotically similar, empirical results reveal that the GLR approach is notably more efficient than the Cox model when the number of subjects is small (< 100 subjects per treatment group). An example based on survival times of cervical cancer patients is used to illustrate the proposed methodology. Copyright © 2001 John Wiley & Sons, Ltd.
Understanding neural networks using regression trees: an application to multiple myeloma survival data
Authors: Faraggi David , LeBlanc Michael , Crowley John 
Published: August 2002

AbstractNeural networks are becoming very popular tools for analysing data. It is however quite difficult to understand the neural network output in terms of the original covariates or input variables. In this paper we provide, using readily available software, an easy way of understanding the output of the neural network using regression trees. We focus on the problem in the context of censored survival data for patients with multiple myeloma, where identifying groups of patients with different prognosis is an important aspect of clinical studies. The use of regression trees to help understand neural networks can be easily applied to uncensored situations. Copyright © 2001 John Wiley & Sons, Ltd.
Mixed multivariate generalized linear models for assessing lower‐limb arterial stenoses
Authors: Cengiz Mehmet A. , Percy David F. 
Published: August 2002

AbstractExperiments and observational studies often involve gathering information on several response variables, enabling us to model their dependence on observable predictor variables. Despite associations between the response variables, they are often analysed separately using general and generalized linear models. This paper investigates applications of multivariate regression analysis to improve the accuracy of predictions and decisions, in the specific context of diagnosing arterial stenoses in human legs. Two basic models are developed for this application, using (i) four binary responses and (ii) a mixture of two binary and two normal responses. The results clearly demonstrate the potential advantages offered by this approach. Copyright © 2001 John Wiley & Sons, Ltd.
A hierarchical regression approach to meta‐analysis of diagnostic test accuracy evaluations
Authors: Rutter Carolyn M. , Gatsonis Constantine A. 
Published: August 2002

AbstractAn important quality of meta‐analytic models for research synthesis is their ability to account for both within‐ and between‐study variability. Currently available meta‐analytic approaches for studies of diagnostic test accuracy work primarily within a fixed‐effects framework. In this paper we describe a hierarchical regression model for meta‐analysis of studies reporting estimates of test sensitivity and specificity. The model allows more between‐ and within‐study variability than fixed‐effect approaches, by allowing both test stringency and test accuracy to vary across studies. It is also possible to examine the effects of study specific covariates. Estimates are computed using Markov Chain Monte Carlo simulation with publicly available software (BUGS). This estimation method allows flexibility in the choice of summary statistics. We demonstrate the advantages of this modelling approach using a recently published meta‐analysis comparing three tests used to detect nodal metastasis of cervical cancer. Copyright © 2001 John Wiley & Sons, Ltd.
An extension of the continual reassessment method using decision theory
Authors: Leung Denis Heng‐Yan , Wang You‐Gan 
Published: August 2002

AbstractThe primary goal of a phase I trial is to find the maximally tolerated dose (MTD) of a treatment. The MTD is usually defined in terms of a tolerable probability, q*, of toxicity. Our objective is to find the highest dose with toxicity risk that does not exceed q*, a criterion that is often desired in designing phase I trials. This criterion differs from that of finding the dose with toxicity risk closest to q*, that is used in methods such as the continual reassessment method. We use the theory of decision processes to find optimal sequential designs that maximize the expected number of patients within the trial allocated to the highest dose with toxicity not exceeding q*, among the doses under consideration. The proposed method is very general in the sense that criteria other than the one considered here can be optimized and that optimal dose assignment can be defined in terms of patients within or outside the trial. It includes as an important special case the continual reassessment method. Numerical study indicates the strategy compares favourably with other phase I designs. Copyright © 2002 John Wiley & Sons, Ltd.
Competitive advantage: logical and philosophical considerations
Authors: Powell Thomas C. 
Published: August 2002

AbstractStrategic management theories invoke the concept of competitive advantage to explain firm performance, and empirical research investigates competitive advantage and describes how it operates. But as a performance hypothesis, competitive advantage has received surprisingly little formal justification, particularly in light of its centrality in strategy research and practice. As it happens, the core hypothesis—that competitive advantage produces sustained superior performance—finds little support in formal deductive or inductive inference, and the leading theories of competitive advantage incorporate refutation barriers that preclude meaningful empirical tests. This article explores the logical and philosophical foundations of the competitive advantage hypothesis, locating its philosophical foundations in the epistemologies of Bayesian induction, abductive inference and an instrumentalist, pragmatic philosophy of science. Copyright © 2001 John Wiley & Sons, Ltd.
An examination into the causal logic of rent generation: contrasting Porter's competitive strategy framework and the resource‐based perspective
Authors: Spanos Yiannis E. , Lioukas Spyros 
Published: August 2002

AbstractIn this study we revisit some fundamental questions that are increasingly at the heart of current strategic management discourse regarding the relative impact of industry and firm‐specific factors on sustainable competitive advantage. We explore this issue by referring to respective assertions of two major perspectives that dominate the literature over the last two decades: the Porter framework of competitive strategy and the more recent resource‐based view of the firm. A composite model is proposed which elaborates upon both perspectives' divergent causal logic with respect to the conditions relevant for firm success.Empirical findings suggest that industry and firm specific effects are both important but explain different dimensions of performance. Where industry forces influence market performance and profitability, firm assets act upon accomplishments in the market arena (i.e., market performance), and via the latter, to profitability. The paper concludes with directions for future research that will seek to integrate both content and process aspects of firm behavior. Copyright © 2001 John Wiley & Sons, Ltd.
Cultural entrepreneurship: stories, legitimacy, and the acquisition of resources
Authors: Lounsbury Michael , Glynn Mary Ann 
Published: August 2002

AbstractWe define cultural entrepreneurship as the process of storytelling that mediates between extant stocks of entrepreneurial resources and subsequent capital acquisition and wealth creation. We propose a framework that focuses on how entrepreneurial stories facilitate the crafting of a new venture identity that serves as a touchstone upon which legitimacy may be conferred by investors, competitors, and consumers, opening up access to new capital and market opportunities. Stories help create competitive advantage for entrepreneurs through focal content shaped by two key forms of entrepreneurial capital: firm‐specific resource capital and industry‐level institutional capital. We illustrate our ideas with anecdotal entrepreneurial stories that range from contemporary high‐technology accounts to the evolution of the mutual fund industry. Propositions are offered to guide future empirical research based on our framework. Theoretically, we aim to extend recent efforts to synthesize strategic and institutional perspectives by incorporating insights from contemporary approaches to culture and organizational identity. Copyright © 2001 John Wiley & Sons, Ltd.
Customer value analysis in a heterogeneous market
Authors: DeSarbo Wayne S. , Jedidi Kamel , Sinha Indrajit 
Published: August 2002

AbstractIn recent years, customer value has become a major focus among strategy researchers and practitioners as an essential element of a firm's competitive strategy. Many firms have been interested in Customer Value Analysis (CVA) which involves a structural analysis of the antecedent factors of perceived value (i.e., perceived quality and perceived price) to assess their relative importance in the perceptions of their buyers. We develop a statistical approach for performing CVA utilizing a recursive simultaneous equation model that is formulated to accommodate buyer heterogeneity. In particular, the proposed finite‐mixture methodology allows one to estimate the relative effects and integration rules of perceived value drivers at the market segment level, as well as to simultaneously determine the (unknown) segments themselves. We demonstrate the utility of the proposed methodology via an actual commercial application involving a large electric utility company. Finally, we discuss the contributions of our research from the perspective of firm strategy and how it may be extended in the future. Copyright © 2001 John Wiley & Sons, Ltd.
The survival of new domestic and foreign‐owned firms
Authors: Mata José , Portugal Pedro 
Published: August 2002

AbstractWe compare the survival of new domestic and foreign‐owned firms. We analyze the determinants of the survival of new firms and investigate whether foreignness accounts for significant differences in the survival of new foreign and new domestic firms. We find survival to be determined by ownership advantages, size and growth strategies, the internal organization of firms, and by industry characteristics such as economies of scale, and industry entry and growth. After controlling for these characteristics, we find that domestic and foreign firms do not exhibit different chances of survival, that they respond in similar fashions to the determinants of survival and display identical time patterns of exit. Copyright © 2002 John Wiley & Sons, Ltd.
Pace, rhythm, and scope: process dependence in building a profitable multinational corporation
Authors: Vermeulen Freek , Barkema Harry 
Published: August 2002

AbstractMany potential benefits of foreign expansion have been identified in the literature, yet empirical support that multinational firms perform better than domestic firms is mixed. This paper takes a longitudinal perspective and argues that how much a firm benefits from having foreign subsidiaries depends on its process of internationalization. We argue that a firm's capacity to absorb expansion is subject to constraints: some expansion patterns increase profitability less than others, owing to diseconomies of time compression. We hypothesize that the speed of internationalization, the spread of the geographical and product markets entered, and the irregularity of the expansion pattern negatively moderate a firm's increase in profitability resulting from international expansion. Model estimations based on panel data raised strong support for these predictions. Copyright © 2002 John Wiley & Sons, Ltd.
Impact of experience on maintenance skills
Authors: Jørgensen Magne , Sjøberg Dag I. K. 
Published: August 2002

AbstractThis study reports results from an empirical study of 54 software maintainers in the software maintenance department of a Norwegian company. The study addresses the relationship between amount of experience and maintenance skills. The findings were, amongst others, as follows. (1) While there may have been a reduction in the frequency of major unexpected problems from tasks solved by very inexperienced to medium experienced maintainers, additional years of general software maintenance experience did not lead to further reduction. More application specific experience, however, further reduced the frequency of major unexpected problems. (2) The most experienced maintainers did not predict maintenance problems better than maintainers with little or medium experience. (3) A simple one‐variable model outperformed the maintainers' predictions of maintenance problems, i.e. the average prediction performance of the maintainers seems poor. An important reason for the weak correlation between length of experience and ability to predict maintenance problems may be the lack of meaningful feedback on the predictions. Copyright © 2002 John Wiley & Sons, Ltd.
Design, implementation and evolution of object oriented frameworks: concepts and guidelines
Authors: van Gurp J. , Bosch J. 
Published: August 2002

AbstractObject‐oriented frameworks provide software developers with the means to build an infrastructure for their applications. Unfortunately, frameworks do not always deliver on their promises of reusability and flexibility. To address this, we have developed a conceptual model for frameworks and a set of guidelines to build object oriented frameworks that adhere to this model. Our guidelines focus on improving the flexibility, reusability and usability (i.e. making it easy to use a framework) of frameworks. Copyright © 2001 John Wiley & Sons, Ltd.
From broadcast television to Internet audio/video: techniques and tools for VCR‐style interactivity
Authors: Makofske David B. , Almeroth Kevin C. 
Published: August 2002

AbstractOne of the new applications evolving in the Internet is streaming audio/video. A major reason for its growing popularity is interest in the compelling new services that become possible. Prototype services are being developed which are new to the Internet but offer the same look, feel, and functionality that have traditionally only been found in services delivered via other communication medium, e.g. broadcast television. In addition, the Internet is evolving to offer ‘value‐added’ services, like streaming audio/video with VCR‐style interactivity and embedded hyperlinks. We are poised both on seeing the development of new paradigms for interacting with audio/video, and on seeing the merging of broadcast television and Internet‐based broadcasts. Before this process can be considered successful, a number of technical challenges, derived from the various ways in which content is physically delivered, must be solved. In this paper, we focus on the value‐added service of VCR interactivity. VCR interactivity has long been a challenge for both broadcast television and streamed Internet audio/video. The challenge is how to provide individualized playout for content being streamed to a large group of users using one‐to‐many delivery. While some new companies are starting to offer devices which provide this kind of service for broadcast television, there are still numerous technical challenges for the Internet‐based version of a similar service. This paper has a three‐fold objective. First, we describe the types of services available in the traditional broadcast infrastructure and compare these to the types of services that are deployed or possible in Internet‐based services. Second, we describe our attempts to implement some of the more challenging and novel service types. In particular, we examine client‐based control of programs streamed over the Internet to tens, thousands, or even millions of users. Finally, we discuss the impact of these services on the protocols and applications used to support Internet‐based, multi‐party conferencing. Copyright © 2001 John Wiley & Sons, Ltd.
Transparent adaptation of sharing granularity in MultiView‐based DSM systems
Authors: Niv Nitzan , Schuster Assaf 
Published: August 2002

AbstractIn this paper we propose a mechanism that provides distributed shared memory (DSM) systems with a flexible sharing granularity. The size of the shared memory units is dynamically determined by the system during runtime. This size can range from that of a single variable up to the size of the entire shared memory space. During runtime, the DSM transparently adapts the granularity to the memory access pattern of the application in each phase of its execution. This adaptation, called ComposedView, provides efficient data sharing in software DSM while preserving sequential consistency. Neither complex code analysis nor annotation by the programmer or the compiler are required. Our experiments indicate a substantial performance boost (up to 80% speed‐up improvement) when running a large set of applications using our method, compared to running these benchmark applications with the best fixed granularity. Copyright © 2001 John Wiley & Sons, Ltd.
View‐based process elicitation: a user's perspective
Authors: Tassé Josée , Madhavji Nazim H. 
Published: August 2002

AbstractSoftware process models are considered important for a number of purposes, such as assessment, improvement and customization. In order to obtain a complete model of a process, it is often necessary to gather relevant information from different sources (agents, documents, observations, etc.). One problem with this is that different sources may give inconsistent information about the same process. Resolving such conflicts can be difficult and arduous. This paper describes a user's perspective of a prototype tool, called V‐elicit, which helps in eliciting process models based on information from multiple sources. In V‐elicit, the information gathered from each source is entered separately as ‘views’, each of which is checked for internal consistency. Following this, common elements across the views are identified, and inconsistencies amongst them are flagged. As the elicitor, aided by the system, resolves these conflicts, the final (merged) model is automatically built. These features are illustrated through an example elicitation of a requirements engineering process. Copyright © 2001 John Wiley & Sons, Ltd.
Adaptation to creation: progress of organizational learning and increasing complexity of learning systems
Authors: Unnikrishnan Nair K. 
Published: August 2002

AbstractA brief survey of organizational learning literature shows that understanding of how organizations learn has proceeded along two streams: one based on progress function or learning/experience curve effect, and the other as a process facilitating organizational adaptation and growth, and development and sustenance of competitiveness. This latter stream presents three phases of evolution: initially it considered learning as adaptation through search and problem solving, followed by attempts at conceptualization of learning as an organization‐wide, holistic phenomenon, and finally focusing on development of systems, processes, training tools, capabilities, etc., for building learning organizations. Learning is now understood as the development of organizational generative capabilities with a wide response range. The article identifies that the understanding of organizational learning from learning as adaptation to information processing and knowledge creation systems capable of generating a wide range of response patterns exhibits an underlying link of increasing complexity. This in turn holds an interesting correspondence to Boulding's hierarchy of systems. The article discusses the implications of this correspondence for research and practice. Copyright © 2001 John Wiley & Sons, Ltd.