NEW EFFICIENT ESTIMATION AND VARIABLE SELECTION METHODS FOR SEMIPARAMETRIC VARYING-COEFFICIENT PARTIALLY LINEAR MODELS

The complexity of semiparametric models poses new challenges to statistical inference and model selection that frequently arise from real applications. In this work, we propose new estimation and variable selection procedures for the semiparametric varying-coefficient partially linear model. We first study quantile regression estimates for the nonparametric varying-coefficient functions and the parametric regression coefficients. To achieve nice efficiency properties, we further develop a semiparametric composite quantile regression procedure. We establish the asymptotic normality of proposed estimators for both the parametric and nonparametric parts and show that the estimators achieve the best convergence rate. Moreover, we show that the proposed method is much more efficient than the least-squares-based method for many non-normal errors and that it only loses a small amount of efficiency for normal errors. In addition, it is shown that the loss in efficiency is at most 11.1% for estimating varying coefficient functions and is no greater than 13.6% for estimating parametric components. To achieve sparsity with high-dimensional covariates, we propose adaptive penalization methods for variable selection in the semiparametric varying-coefficient partially linear model and prove that the methods possess the oracle property. Extensive Monte Carlo simulation studies are conducted to examine the finite-sample performance of the proposed procedures. Finally, we apply the new methods to analyze the plasma beta-carotene level data.     

Recommendations on the statistical analysis of the Comet assay

In 2010, the Statisticians in the Pharmaceutical Industry (PSI) Toxicology Special Interest Group met to discuss the design and analysis of the Comet assay. The Comet assay is one potential component of the package of safety studies required by regulatory bodies. As these studies usually involve a three-way nested experimental design and as the distribution of the measured response is usually either lognormal or lognormal plus a point mass at zero, the analysis is not straightforward. This has led to many different types of analysis being proposed in the literature, with several different methods applied within the pharmaceutical industry itself. This article summarises the PSI Toxicology Group's discussions and recommendations around these issues.     

Older Women's Health and Its Impact on Wealth

As many elderly women tend to outlive their spouses, there is a growing population of unmarried elderly women. Unmarried women are worse off than married women both financially and physically. A question that has not been answered is whether and how the relationship between health and wealth differs across elderly women's marital status. Do the negative impacts of health problems cause more serious financial consequences for unmarried elderly women than married women? Using the five waves of data from the Asset and Health Dynamics Among the Oldest Old (AHEAD) from 1993 to 2002, this question is empirically investigated. Results indicate that severe chronic conditions result in 4 to 10% greater wealth depletion for unmarried women than married women. This finding calls for heightened awareness of the negative financial consequences of health problems and also calls for increased lifetime earning potential, reconsideration of women's retirement benefits, and greater attention to preventive care.     

Trends in old-age functioning and disability in Japan, 1993-2002

Disability is a burden to individuals and society. Population ageing, combined with the fact that disability is most common among the elderly, has focused attention on trends in old-age disability. This study estimates trends in functioning and disability among Japanese elderly from 1993 to 2002 and contrasts the patterns with those found in the USA. Japan is an especially interesting country because its age structure is relatively old, and it currently has the highest life expectancy in the world despite the fact that just 50 years ago its life expectancy was in the bottom half of all countries. As in the USA, disability rates have fallen. If it were not for the gains in disability between 1993 and 2002, there would have been 1.1 million more disabled elderly in 2002. The reductions were experienced broadly across socio-demographic and economic groups. Increases in education across cohorts are associated with the declines in disability.     

Homogamy and Intermarriage of Japanese and Japanese Americans With Whites Surrounding World War II

Although some sociologists have suggested that Japanese Americans quickly assimilated into mainstream America, scholars of Japanese America have highlighted the heightened exclusion that the group experienced. This study tracked historical shifts in the exclusion level of Japanese and Japanese Americans in the United States surrounding World War II with homogamy and intermarriage with Whites for the prewar (1930-1940) and resettlement (1946-1966) marriage cohorts. The authors applied log-linear models to census microsamples (N = 1,590,416) to estimate the odds ratios of homogamy versus intermarriage. The unadjusted odds ratios of Japanese Americans declined between cohorts and appeared to be consistent with the assimilation hypothesis. Once compositional influences and educational pairing patterns were adjusted, however, the odds ratios increased and supported the heightened exclusion hypothesis.     

Effect of Berkson measurement error on parameter estimates in Cox regression models

We study the effect of additive and multiplicative Berkson measurement error in Cox proportional hazard model. By plotting the true and the observed survivor function and the true and the observed hazard function dependent on the exposure one can get ideas about the effect of this type of error on the estimation of the slope parameter corresponding to the variable measured with error. As an example, we analyze the measurement error in the situation of the German Uranium Miners Cohort Study both with graphical methods and with a simulation study. We do not see a substantial bias in the presence of small measurement error and in the rare disease case. Even the effect of a Berkson measurement error with high variance, which is not unrealistic in our example, is a negligible attenuation of the observed effect. However, this effect is more pronounced for multiplicative measurement error.     

The effects of religion, superstition, and perceived gender inequality on the degree of suicide intent: a study of serious attempters in China

Previous studies have tried to account for the uniqueness of gender ratios in Chinese suicide through physiological and psychological differences between men and women, and the means employed in the fatal act. From the point of view of the socio-psychological traits, this study examines the effects of religion (religiosity), superstition, and perceived gender inequality among Chinese women on the degree of their suicide intent. A four-page structured interviews were performed to the consecutively sampled serious attempters of suicide hospitalized to emergency rooms immediately after the suicidal act in Dalian areas, China. Both univariate analyses and the multiple regression model have found that the higher the degree the religiosity and superstition on metempsychosis, the stronger the suicide intent Chinese women had. The perceived gender inequality is positively correlated with suicide intent, and it is especially true for Chinese women. The socio-psychological traits and traditional culture values and norms have important impacts on suicide patterns in Chinese societies.     

马列主义经典作家论人类社会与自然的相互关系

马克思列宁主义经典作家在其著作中最全面地揭示了不同社会经济条件下社会和自然相互关系的诸问题。人类对于自然界的态度是哲学的核心问题之一,即人类认识整个现实的一个最重要的观点。马克思列宁主义经典作家曾经强调指出:“只要有人存在,自然史和人类史就彼此相互制约着”。     

补充能量饲料和季节对Moxoto山羊血清免疫球蛋白和总蛋白含量的影响

巴西东北部属半干旱气候,通常1—5月是雨季,6—12月是旱季。在雨季,天然牧草丰富,质量优良,保证了家畜生产(Schacht等,1980)。但到了旱季,牧草量减少,营养严重缺乏,导致山羊体重减轻、死亡、繁殖性能下降和小山羊死亡率上升等(Pfister等,1983;Kawas等,1987a,b)。因此研究补充能量饲料水平对于改善巴西东北地区山羊繁殖性能、增重和健康状况很有必要。     

坦桑尼亚的部族

坦桑尼亚的部族及其分布坦桑尼亚地处东非,位于非洲三大湖和印度洋之间,靠近赤道南侧。坦桑尼亚是一个多部族的国家,除已加入坦桑尼亚国籍的欧洲人和亚洲人外,全国大约有120个部族,分布在坦桑尼亚辽阔的国土上。在这些部族中,就血统而言,除少数外,绝大部分属班图血统。现居住在维多