A Bayesian model for longitudinal count data with non-ignorable dropout

Asthma is an important chronic disease of childhood. An intervention programme for managing asthma was designed on principles of self-regulation and was evaluated by a randomized longitudinal study.The study focused on several outcomes, and, typically, missing data remained a pervasive problem. We develop a pattern-mixture model to evaluate the outcome of intervention on the number of hospitalizations with non-ignorable dropouts. Pattern-mixture models are not generally identifiable as no data may be available to estimate a number of model parameters. Sensitivity analyses are performed by imposing structures on the unidentified parameters.We propose a parameterization which permits sensitivity analyses on clustered longitudinal count data that have missing values due to non-ignorable missing data mechanisms. This parameterization is expressed as ratios between event rates across missing data patterns and the observed data pattern and thus measures departures from an ignorable missing data mechanism. Sensitivity analyses are performed within a Bayesian framework by averaging over different prior distributions on the event ratios. This model has the advantage of providing an intuitive and flexible framework for incorporating the uncertainty of the missing data mechanism in the final analysis.     

Efficacy of a web-based, tailored, alcohol prevention/intervention program for college students: 3-month follow-up

This study presents the results of an efficacy evaluation of a web-based brief motivational alcohol prevention/intervention program called Michigan Prevention and Alcohol Safety for Students (M-PASS). Four on-line sessions providing individually-tailored feedback were delivered to first-year college students over 9 weeks. Non- and low-risk drinking participants received risk prevention, while high-risk drinking participants received a risk-reduction intervention. Both intervention and control groups were surveyed at baseline and at a 3-month follow-up. Analysis showed positive effects for both men and women on stage of change, drinking behavior, drinking motivation and attitudes, and use of risk-reduction strategies. These results provided evidence of efficacy and found that M-PASS had both intervention and prevention effects, making it unique among currently developed brief alcohol interventions for college students.     

A MACROECONOMIC MODEL ON THE QUALITY OF GOVERNMENT AND ECONOMIC PERFORMANCE

We determine the relative rewards to producers, private rent‐seekers, and bureaucrats and allocation of talent between them in a general equilibrium model. Unproductive activity creates a negative externality on the relative rewards to producers. If the size of bureaucracy is exogenously given, among the multiple equilibria, the one with fewer private rent‐seekers yields higher welfare. By choosing a small size of bureaucracy, the government can establish the superior equilibrium as the unique outcome, which also achieves the constrained optimum. If the population of bureaucrats is endogenously determined, however, a larger bureaucracy enhances production and welfare. The size of government and economic performance are jointly determined, and their relationship depends on the quality of government. Our result supports the view that the size of government may not matter much; what is important is the quality of government. (JEL E60, E61, H00)     

Sourcing Information Security Operations: The Role of Risk Interdependency and Competitive Externality in Outsourcing Decisions

Firms are increasingly outsourcing information security operations to managed security service providers (MSSPs). Cost reduction and quality (security) improvement are often mentioned as motives for outsourcing information security, and these are also the frequently cited reasons for outsourcing traditional information technology (IT) functions, such as software development and maintenance. In this study, we present a different explanation—one based on interdependent risks and competitive externalities associated with IT security—for firms' decisions to outsource security. We show that in the absence of competitive externalities and interdependent risks, a firm will outsource security if and only if the MSSP offers a quality advantage over in‐house operations, which is consistent with the conventional explanation for security outsourcing. However, when security risks are interdependent and breaches impose competitive externalities, although firms still have stronger incentive to outsource security if the MSSP offers a higher quality in terms of preventing breaches than in‐house management, a quality advantage of MSSP over in‐house management is neither a prerequisite for a firm to outsource security nor a guarantee that a firm will. In addition to MSSP quality, the type of externality (positive or negative), the degree of externality, whether outsourcing increases or decreases risk interdependency, and the breach characteristics determine firms' sourcing decisions. When security breaches impose a positive externality, the incentive to outsource is enhanced if the MSSP decreases the risk interdependency and diminished if the MSSP increases this interdependency. A negative externality has the opposite effect on firms' incentives to outsource. A high demand spillover to a competitor, together with a high loss in industry demand because of a security breach, enhances these incentives to outsource security operations when the externality is negative. Finally, we extend our base model in several dimensions and show that our main results regarding the impact of interdependent risks and competitive externalities on sourcing decisions are robust and generalizable to different specifications.     

课程文化的内涵分析

课程文化的实质,是课程文化最根本、最深层、最终极的规定性.以往的研究侧重从课程的角度或文化的角度来理解课程文化的内涵,应该说这是理解课程文化内涵的一种视角.本文从课程与文化两个概念的共同属性来把握课程文化的内涵.它是主体发展的文化资源.     

Efficacy of a Web-Based,Tailored, Alcohol Prevention/Intervention Program for College Students: Initial Findings

Abstract

Objective: Reduce college student at-risk drinking (ARD) using a Web-based brief motivational alcohol prevention/intervention called Michigan Prevention and Alcohol Safety for Students (M-PASS). Participants: Participants included 1,137 randomly sampled first-year college students, including 59% female, 80% white, and averaged age 18.1 years. Methods: Intervention group participants (n = 616) attended 4 online M-PASS sessions, receiving feedback tailored to individual drinking patterns and concepts from 4 behavior change theories. Control group participants (n = 521) completed a mid-phase survey, and both groups were surveyed at baseline and posttest. Results: Evidence of M-PASS's efficacy was found. The intervention was associated with advanced stage of change, lower tolerance of drinking and drink/driving, fewer reasons to drink, and use of more strategies to avoid ARD. Preliminary evidence of behavioral change was also found. Efficacy was greater for women than men. Conclusions: Web-based programs may be useful in reducing alcohol-related risk among college students. Further evaluation is needed.     

Demand Forecast Sharing in Supply Chains

This paper examines the incentives of a manufacturer and a retailer to share their demand forecasts. The demand at the retailer is a linearly decreasing function of price. The manufacturer sets the wholesale price first, and the retailer sets the retail price after observing the wholesale price. Both players set their prices based on their forecasts of demand. In the make‐to‐order scenario, the manufacturer sets the production quantity after observing the actual demand; in the make‐to‐stock scenario, the manufacturer sets the production quantity before the demand is realized. In the make‐to‐order scenario, we show that sharing the forecast unconditionally by the retailer with the manufacturer benefits the manufacturer but hurts the retailer. We also demonstrate that a side payment contract cannot induce Pareto‐optimal information sharing equilibrium, but a discount based wholesale price contract can. The social welfare as well as consumer surplus is higher under the discount contract, compared with under no information sharing. In the make‐to‐stock scenario, the manufacturer realizes additional benefits in the form of savings in inventory holding and shortage costs when forecasts are shared. If the savings from inventory holding and shortage costs because of information sharing are sufficiently high, then a side payment contract that induces Pareto‐optimal information sharing is feasible in the make‐to‐stock scenario. We also provide additional managerial insights with the help of a computational study.     

晚清数学的发展

晚清数学的发展主要是由技术进步的派生需求引导的,数学发展的目标与中体西用的要求之间存在冲突,这种矛盾最终导致中国数学的全盘西化。西学东渐改变了中算知识的结构却未能改变知识价值的结构,数学会通的效率受到考核技术的制约,考核技术的水平受到中体西用的制约。数学概念的进化因而受到阻碍,会通工作陷入效益递减的境地,最终导致中算被完全取代。     

试论美国内战期间林肯政府的外交政策

美国内战是美国历史上北方资本主义制度战胜南方奴隶制度的一场正义的、进步的战争。内战本属美国内部问题,但由于战争结局会影响到欧洲列强的既得利益,因而北方的林肯政府在内战中不得不面对当时极　　　　其复杂的国际关系。我们认为,北方之最终获胜固然在于其正义性,但林肯政府灵活、有效的外交策略,同样功不可没。本文将重点探讨美国内战的国际关系及林肯政府的外支政策。