Comparing two measures of creatinine clearance: an application of errors-in-variables and bootstrap techniques

Two indices of creatinine clearance (an index of kidney function) are compared on a group of cancer patients who underwent chemotherapy with a potentially nephrotoxic drug. The standard index, measured creatinine clearance MCC, is cumbersome to use, whereas the more convenient alternative, estimated creatinine clearance ECC, has not yet been conclusively evaluated on cancer patients. We conclude that under certain clinical conditions ECC and MCC are identically calibrated for males, but not for females, and we obtain estimated true and false positive rates for assessing the use of ECC instead of MCC as a diagnostic tool. We use a model that is formally equivalent to an errors-in-variables model with (unbalanced) repeated observations and correlated measurement errors. The bootstrap is used to obtain standard errors and confidence limits.     

Parental Involvement Laws and Minor and Non-Minor Teen Abortion and Birth Rates

The effects of parental notice and consent laws on abortion and birth rates were analyzed for two groups of teens: those 15 to 17 years old (i.e., minor teens) and those 18 to 19 years old (i.e., non-minor teens). Twelve states report abortion and birth statistics at the county level for these two age groups. The sample consists of 597 counties from these twelve states. Residence county abortion and birth rates were regressed against parental notice laws, parental consent laws, and several control variables (i.e., type of state public funding, population density, education and income levels, unemployment rate, family stability, extent of poverty, church membership, and geographic region).An important finding of this study is that both parental consent and notification laws were related to significantly lower abortion rates and to significantly higher birth rates for both minor and non-minor teens. Three measures (i.e., church membership, family stability, and education level) were related negatively and significantly to minor and non-minor teens' abortion rates and birth rates. One other measure (i.e., restrictive public funding) was related significantly to lower abortion rates and higher birth rates for minor and non-minor teens.     

Bayesian and likelihood inference for cure rates based on defective inverse Gaussian regression models

Failure time models are considered when there is a subpopulation of individuals that is immune, or not susceptible, to an event of interest. Such models are of considerable interest in biostatistics. The most common approach is to postulate a proportion p of immunes or long-term survivors and to use a mixture model [5]. This paper introduces the defective inverse Gaussian model as a cure model and examines the use of the Gibbs sampler together with a data augmentation algorithm to study Bayesian inferences both for the cured fraction and the regression parameters. The results of the Bayesian and likelihood approaches are illustrated on two real data sets.     

基于多阶段随机规划模型的国债动态积极投资策略

本文提出国债组合投资的多阶段随机规划模型,导出基于未来利率市场不确定信息的具备动态调整特点的国债组合主动投资策略。该模型采用基于利率水平、斜率和曲率"三位一体"的离散情景树刻画未来利率期限结构动态演化过程,其中特别考虑了广义货币供给变动的影响;通过最小化国债组合收益的条件风险价值,对国债组合进行主动动态调整;同时兼顾国债投资安全性、流动性和收益性等要求,实现了国债组合投资管理中利率风险规避和收益能力的有效匹配。实证研究表明,与传统久期配比免疫模型相比,该模型确定的最优策略不仅能够为国债组合提供更强的抵御利率风险能力,而且能够稳步提升其收益空间,为金融机构实现国债投资的主动管理提供决策支持。     

Real‐Time Delay Estimation Based on Delay History in Many‐Server Service Systems with Time‐Varying Arrivals

Motivated by interest in making delay announcements in service systems, we study real‐time delay estimators in many‐server service systems, both with and without customer abandonment. Our main contribution here is to consider the realistic feature of time‐varying arrival rates. We focus especially on delay estimators exploiting recent customer delay history. We show that time‐varying arrival rates can introduce significant estimation bias in delay‐history‐based delay estimators when the system experiences alternating periods of overload and underload. We then introduce refined delay‐history estimators that effectively cope with time‐varying arrival rates together with non‐exponential service‐time and abandonment‐time distributions, which are often observed in practice. We use computer simulation to verify that our proposed estimators outperform several natural alternatives.     

我国商业银行存贷差扩大原因的实证分析

选取城乡居民储蓄率等作为存贷差扩大影响因素的解释变量,运用单位根检验、协整检验和误差修正模型等统计方法对数据进行相应的分析,结果表明,所选解释变量对存贷差的扩大都存在长期影响关系。针对这些对存贷差扩大有影响的因素制定相应的货币政策和财政政策,为构建和谐社会提供一个坚实的资金保障系统。     

Strategic technology alliance termination: An empirical investigation

There is growing consensus that overall alliance termination rates are high. However, despite this track record of termination and despite unsurpassed growth rates of strategic technology alliances, little is known about the reasons for their termination. Typically strategic alliances have been characterized as inherently instable, i.e. often involving unplanned and premature termination of the alliance by partnering firms indicating alliance failure. The literature on strategic technology alliances, however, proposes that alliance termination does not always indicate failure, but can be intended and can be a sign of strength. We examine these different perceptions by using a sample of 48 strategic technology alliances in different high-technology industries. The findings in the paper confirm that the rates of termination are rather high for strategic technology alliances. Overall, we found that in particular negative prospects about future cooperation, negative perceptions about joint benefits and the lack of a win-win situation had an impact on the decision to terminate a strategic technology alliance. Also, the fact that some companies opt only for short-term (not for long-term and renewed) cooperation seems to introduce a negative factor into the longevity of strategic technology alliances.     

The supplier selection problem with quantity discounts and truckload shipping

To minimize procurement expenditures both purchasing and transportation costs need to be considered. We study a procurement setting in which a company needs to purchase a number of products from a set of suppliers to satisfy customer demand. The suppliers offer total quantity discounts and transportation costs are based on truckload shipping rates. The goal is to select a set of suppliers so as to satisfy product demand at minimal total costs. The resulting optimization problem is strongly NP-hard. We develop integer programming based heuristics to solve the problem. Extensive computational experiments demonstrate the efficacy of the proposed heuristics and provide insight into the impact of instance characteristics on effective procurement strategies.     

U.S. Family Household Momentum and Dynamics: An Extension and Application of the ProFamy Method

The classic headship-rate method for demographic projections of households is not linked to demographic rates, projects a few household types without size, and does not deal with household members other than heads. By comparison, the ProFamy method uses demographic rates as input and projects more detailed household types, sizes, and living arrangements for all members of the population. Tests of projections from 1990 to 2000 using ProFamy and based on observed U.S. demographic rates before 1991 show that discrepancies between our projections and census observations in 2000 are reasonably small, validating the new method. Using data from national surveys and vital statistics, census microfiles, and the ProFamy method, we prepare projections of U.S. households from 2000 to 2050. Medium projections as well as projections based on smaller and larger family scenarios with corresponding combinations of assumptions of marriage/union formation and dissolution, fertility, mortality, and international migration are performed to analyze future trends of U.S. households and their possible higher and lower bounds, as well as enormous racial differentials. To our knowledge, the household projections reported in this article are the first to have found empirical evidence of family household momentum and to have provided informative low and high bounds of various indices of projected future households and living arrangements distributions based on possible changes in demographic parameters.     

基于公司治理因素的财务困境预警实证研究

在对财务困境预警领域已有研究成果进行总结和评价的基础上,选取我国沪、深两市2007、2008年被ST的70家公司,及与其上市时间及主营业务相近的70家非ST公司,提取财务指标及有关治理指标对上市公司财务困境进行预警研究。实证研究结果表明：将公司治理因素引入预警模型能够提高预警的准确程度,财务困境预警研究综合考虑财务指标和治理指标具有积极意义。