Penalized spline joint models for longitudinal and time-to-event data

The joint models for longitudinal data and time-to-event data have recently received numerous attention in clinical and epidemiologic studies. Our interest is in modeling the relationship between event time outcomes and internal time-dependent covariates. In practice, the longitudinal responses often show non linear and fluctuated curves. Therefore, the main aim of this paper is to use penalized splines with a truncated polynomial basis to parameterize the non linear longitudinal process. Then, the linear mixed-effects model is applied to subject-specific curves and to control the smoothing. The association between the dropout process and longitudinal outcomes is modeled through a proportional hazard model. Two types of baseline risk functions are considered, namely a Gompertz distribution and a piecewise constant model. The resulting models are referred to as penalized spline joint models; an extension of the standard joint models. The expectation conditional maximization (ECM) algorithm is applied to estimate the parameters in the proposed models. To validate the proposed algorithm, extensive simulation studies were implemented followed by a case study. In summary, the penalized spline joint models provide a new approach for joint models that have improved the existing standard joint models.     

GAMES AND TRUTHS: Learning To Construct Social Problems In High School Debate

Although social constructionists have taken the process by which people learn to present social problems for granted, these skills are acquired in the course of socialization. Through high school debate, adolescents acquire techniques for making arguments, using evidence, and presenting claims to multiple audiences. In the process, they learn that taking a public position does not necessarily require a deeply held commitment. This model resonates with the institutional structure of politics and law in the United States in which adversaries battle each other in a rule-governed "game,'a contest ultimately evaluated by judges assumed to be impartial. To understand the process by which adolescents gain the skills to construct social problems, I conducted an ethnographic study of debate teams at two high schools. The ability to take both sides of an argument, express ideas with which one does not personally agree, and present powerful, if questionable, evidence, constrained by time, teaches teenagers how to engage in social problem discourse and provides a training ground for moral entrepreneurs.     

Introduction: “There Is a Person Here”: An Interview with Judith Butler

In this interview, the coeditors, along with other contributors, ask Judith Butler a variety of questions regarding queer theory, gender identities, scientific and legal discourse, bodily abjection, race and class positioning, and political organizing. This range of subject matter suggests not only the breadth of Butler's work, but also its applicability to any number of people, whose relation to theory ranges from highly politicized to politically indifferent. The interview demonstrates the responsiveness of Butler's work to cultural translation and political action.     

A regional solution to the strategy and structure of multinationals

The transnational solution developed by Bartlett and Ghoshal is shown to be suitable for only a few special cases of multinational enterprise (MNE) strategy and structure. As MNEs have most of their assets and sales within their home region, they are in need of regional, not transnational strategy and structure. Here we provide data on the regional dimension of assets and sales of the world’s largest 500 multinationals. We explore how the empirical reality of a regional concentration of assets and sales imposes a regional solution, rather than the transnational solution.     

Demographic change, macroeconomic conditions, and the murder rate: The case of the United States, 1934–2006

Fluctuations in aggregate crime rates contrary to recent shifts in the age distribution of the U.S. population have cast doubt on the predictive power of the age–crime hypothesis. By examining a longer time horizon, back to the early 1930s, we show that the percentage of the young population is a robust predictor of the observed large swings in the U.S. murder rate over time. However, changes in the misery index—the sum of the inflation and unemployment rates—significantly contribute to explaining changes in the murder rate. This applies, in particular, to those changes that are at odds with the long-run trend of the U.S. age distribution, such as the decline in the murder rate in the latter part of the 1970s or its increase starting around the middle of the 1980s.     

Identifiable finite mixtures of location models for clustering mixed-mode data

For clustering mixed categorical and continuous data, Lawrence and Krzanowski (1996) proposed a finite mixture model in which component densities conform to the location model. In the graphical models literature the location model is known as the homogeneous Conditional Gaussian model. In this paper it is shown that their model is not identifiable without imposing additional restrictions. Specifically, for g groups and m locations, (g!)m–1 distinct sets of parameter values (not including permutations of the group mixing parameters) produce the same likelihood function. Excessive shrinkage of parameter estimates in a simulation experiment reported by Lawrence and Krzanowski (1996) is shown to be an artifact of the model's non-identifiability. Identifiable finite mixture models can be obtained by imposing restrictions on the conditional means of the continuous variables. These new identified models are assessed in simulation experiments. The conditional mean structure of the continuous variables in the restricted location mixture models is similar to that in the underlying variable mixture models proposed by Everitt (1988), but the restricted location mixture models are more computationally tractable.     

Project Success: A Multidimensional Strategic Concept

This article presents projects as powerful strategic weapons, initiated to create economic value and competitive advantage. It suggests that project managers are the new strategic leaders, who must take on total responsibility for project business results. Defining and assessing project success is therefore a strategic management concept, which should help align project efforts with the short- and long-term goals of the organization. While this concept seems simple and intuitive, there is very little agreement in previous studies as to what really constitutes project success. Traditionally, projects were perceived as successful when they met time, budget, and performance goals. However, many would agree that there is more to project success than meeting time and budget. The object of this study was to develop a multidimensional framework for assessing project success, showing how different dimensions mean different things to different stakeholders at different times and for different projects. Given the complexity of this question, a combination of qualitative and quantitative methods and two data sets were used. The analysis identified four major distinct success dimensions: (1) project efficiency, (2) impact on the customer, (3) direct business and organizational success, and (4) preparing for the future. The importance of the dimensions varies according to time and the level of technological uncertainty involved in the project. The article demonstrates how these dimensions should be addressed during the project’s definition, planning, and execution phases, and provides a set of guidelines for project managers and senior managers, as well as suggestions for further research.