On trends and constants in periodic autoregressions

Periodic autoregressions are characterised by autoregressive structures that vary with the season. If a time series is periodically integrated, one needs a seasonally varying differencing filter to remove the stochastic trend. When the periodic regression model contains constants and trends with unrestricted parameters, the data can show diverging seasonal deterministic trends. In this paper we derive explicit expressions for parameter restrictions that result in common deterministic trends under periodic trend stationarity and periodic integration.     

Child maltreatment and foster care

In “Child Maltreatment and Foster Care,” Richard J. Gelles, a professor at the University of Pennsylvania School of Social Work, reports what is known about the incidence of child maltreatment and foster care placement rates since welfare reform. He relies on four major sources of data: Current Trends in Child Abuse Reporting and Fatalities: Results of the 1998 Annual Fifty State Survey, the National Child Abuse and Neglect Data System (NCANDS), the National Incidence Survey of Reported and Recognized Child Maltreatment (NIS), and the Voluntary Cooperative Information System (VCIS).     

Classroom sex composition and first-grade school outcomes: The role of classroom behavior

Using nationally representative data from the Early Childhood Longitudinal Study-Kindergarten Cohort (N = 21,409; 10,452 girls and 10,957 boys; mean age = 7.24 years), the association between first-grade classroom sex composition (CSC), measured as the percentage of female students, and end of the year academic (reading, mathematics) and socio-emotional (externalizing problems, internalizing problems, self-control, interpersonal skills) outcomes was examined. Using multilevel modeling techniques and controlling for prior achievement levels, CSC was positively associated with children’s reading achievement at the end of first grade; students performed better in reading in classes with a higher percentage of female students. CSC was also associated with three of the socio-emotional outcomes; controlling for prior levels, students in classrooms with a higher percentage of girls had better self-control and interpersonal skills and fewer internalizing problems. Classroom behavior mediated the effects of CSC on reading achievement and the socio-emotional outcomes. Implications for the composition of first-grade classrooms are discussed.     

Residualization is not the answer: Rethinking how to address multicollinearity

Here I show that a commonly used procedure to address problems stemming from collinearity and multicollinearity among independent variables in regression analysis, “residualization”, leads to biased coefficient and standard error estimates and does not address the fundamental problem of collinearity, which is a lack of information. I demonstrate this using visual representations of collinearity, hypothetical experimental designs, and analyses of both artificial and real world data. I conclude by noting the importance of examining methodological practices to ensure that their validity can be established based on rational criteria.     

The complementarity of internal integration and product modularity: An empirical study of their interaction effect on competitive capabilities

Modular product design and internal integration are commonly adopted by manufacturers to improve operational performance. A number of studies argue that the adoption of product modularity significantly alters organization design, which affects the impact of internal integration on competitive capabilities. This paper thus aims to empirically explore the individual effects as well as interaction effects of product modularity and internal integration on competitive capabilities. The competitive capabilities studied in this paper include product innovativeness, low price, product quality, delivery, flexibility and customer services. After analysing the data from 251 Hong Kong manufacturers through moderated multiple regression analysis, the study found that better internal integration can significantly improve product innovativeness, product quality, delivery, flexibility and customer services, while a high level of product modularity enhances product innovativeness, flexibility and customer services. More importantly, the study shows that internal integration and product modularity can interact to improve product innovativeness and product quality. These results enhance our understanding of the interaction of product design and organizational coordination.     

The Role of Race in Forecasts of Violent Crime

This paper addresses the role of race in forecasts of failure on probation or parole. Failure is defined as committing a homicide or attempted homicide or being the victim of a homicide or an attempted homicide. These are very rare events in the population of individuals studied, which can make these outcomes extremely difficult to forecast accurately. Building in the relative costs of false positives and false negatives, machine learning procedures are applied to construct useful forecasts. The central question addressed is what role race should play as a predictor when as an empirical matter the majority of perpetrators and victims are young, African American, males.     

《欧洲思想起源》导论

从古希腊早期哲学家话语研究欧洲思想的起源是不够的,那是传统大树上的枝杈而非根脉。荷马史诗在某种程度上呈现出最早的希腊人的真实历史样貌,其中充满着后世文明人难以理解的野蛮因素。有关神话与传说的知识是重建文明发生过程的主要素材,是将石器时代与文明时代相连接的认知通道。《伊里亚特》《奥德赛》所透露的生活方式和思维方式像一座永久的历史记忆之丰碑,是我们现在所掌握的最早描写欧洲的生活和思想的活的教材。