Models for the analysis of C-reactive protein in statin trials

Elevation in C-reactive protein (CRP) is an independent risk factor for cardiovascular disease progression and levels are reduced by treatment with statins. However, on-treatment CRP, given baseline CRP and treatment, is not normally distributed and outliers exist even when transformations are applied. Although classical non-parametric tests address some of these issues, they do not enable straightforward inclusion of covariate information. The aims of this study were to produce a model that improved efficiency and accuracy of analysis of CRP data. Estimation of treatment effects and identification of outliers were addressed using controlled trials of rosuvastatin. The robust statistical technique of MM-estimation was used to fit models to data in the presence of outliers and was compared with least-squares estimation. To develop the model, appropriate transformations of the response and baseline variables were selected. The model was used to investigate how on-treatment CRP related to baseline CRP and estimated treatment effects with rosuvastatin. On comparing least-squares and MM-estimation, MM-estimation was superior to least-squares estimation in that parameter estimates were more efficient and outliers were clearly identified. Relative reductions in CRP were higher at higher baseline CRP levels. There was also evidence of a dose-response relationship between CRP reductions from baseline and rosuvastatin. Several large outliers were identified, although there did not appear to be any relationships between the incidence of outliers and treatments. In conclusion, using robust estimation to model CRP data is superior to least-squares estimation and non-parametric tests in terms of efficiency, outlier identification and the ability to include covariate information.     

Missing item imputation for quality-of-life instruments with application to asthma quality-of-life questionnaires

There has been increasing use of quality-of-life (QoL) instruments in drug development. Missing item values often occur in QoL data. A common approach to solve this problem is to impute the missing values before scoring. Several imputation procedures, such as imputing with the most correlated item and imputing with a row/column model or an item response model, have been proposed. We examine these procedures using data from two clinical trials, in which the original asthma quality-of-life questionnaire (AQLQ) and the miniAQLQ were used. We propose two modifications to existing procedures: truncating the imputed values to eliminate outliers and using the proportional odds model as the item response model for imputation. We also propose a novel imputation method based on a semi-parametric beta regression so that the imputed value is always in the correct range and illustrate how this approach can easily be implemented in commonly used statistical software. To compare these approaches, we deleted 5% of item values in the data according to three different missingness mechanisms, imputed them using these approaches and compared the imputed values with the true values. Our comparison showed that the row/column-model-based imputation with truncation generally performed better, whereas our new approach had better performance under a number scenarios.     

Profile information matrix for nonlinear transformation models

For semiparametric models, interval estimation and hypothesis testing based on the information matrix for the full model is a challenge because of potentially unlimited dimension. Use of the profile information matrix for a small set of parameters of interest is an appealing alternative. Existing approaches for the estimation of the profile information matrix are either subject to the curse of dimensionality, or are ad-hoc and approximate and can be unstable and numerically inefficient. We propose a numerically stable and efficient algorithm that delivers an exact observed profile information matrix for regression coefficients for the class of Nonlinear Transformation Models [A. Tsodikov (2003) J R Statist Soc Ser B 65:759-774]. The algorithm deals with the curse of dimensionality and requires neither large matrix inverses nor explicit expressions for the profile surface.     

苏联民族学近五年的回顾与前瞻

苏联民族学正处于两个五年计划之交,应当对它前五年的发展作一主要总结,为后五年的民族学研究勾画出基本的发展前景。前五年,苏联民族学保持了传统民族学作为历史知识的一个专门领域的优良成果,在从广泛的历史角度认识和阐述当代世界的族体一民族过程及其发展预测方面,迈出了明显的一步。同时,它和人类学、民俗学、社会学、地理学、人口学、医学、心理学等学科之间,发展了广泛的联系。对民族学理论问题的研究更加重视。研究方法扩展了,丰富了。群众性调查、预测、资料的电脑处理等,尤其得到广泛运用。苏联民族学家从民族学是关于民族(народ—зтнос)·的科学这一观点出发,继续深入研究了本学科的一般理论问题。民族理论的一些重要方面,如确定民族在其他人类共同体中     

拉克代夫群岛的历史与居民

地处阿拉伯海怀抱的拉克代夫群岛属印度最小的中央直辖区,是由36个小小的珊瑚岛组成。虽然从外表看来似乎默默无闻,但实际上它却具有强烈的吸引力和独特的重要性。拉克代夫群岛总面积并不大,只有32平方公里。但是,如果将它附近的大约4200平方公里的累恭(Legūna)地区(即被珊瑚礁     

阿布哈兹人的生育习俗和礼仪

同孩子的生命(包括孩子出生)有关的习俗和礼仪跟结婚仪式一样,在民族学著作中通常被看成是一系列特殊的家庭礼仪,这些仪礼只有一个目的,即保障社会新成员平安出世及生活顺利。目前还没有描述阿布哈兹人生儿育女的一系列习俗和礼仪的专门著作。本文在某种程度上填补了这个空白。它是在作者对阿布哈兹人的日常生活进行多年观察的基础上写出来的,同时还利用了1982年收集到的实地考察资料。孩子出生在阿布哈兹人家里被看作是极为重要的事情。特别高兴的是生了儿子,人们把他看作是     

Differences by gender, ethnicity, and acculturation in the efficacy of the keepin' it REAL model prevention program

This study examined whether the efficacy of keepin' it REAL, a model program for substance use prevention in schools, was moderated by gender, ethnicity, and acculturation. Gender differences in program efficacy may arise through boys' higher risk of drug use, inadequate attention to girls' developmental issues, or cultural factors like polarized gender expectations. Data came from a randomized trial in 35 Phoenix, Arizona, middle schools involving 4,622 mostly Latino 7th graders. Using multi-level mixed models and multiple imputation missing techniques, results for the total sample showed no gender differences in program effects on recent substance use, but the program was more effective in fostering boys' than girls' anti-drug norms. Subgroup analyses demonstrated several more beneficial program effects for boys than girls (less alcohol and cigarette use and stronger anti-drug norms), but only among less acculturated Latinos. There were no gender differences in program effects among more acculturated Latinos, nor among non-Latino whites.     

Analysis of strategic plans to assess planning for sustainability of comprehensive community initiatives

In order to achieve the intended impact on a community, comprehensive community initiatives must sustain programs once they have been implemented. However, planning for sustainability is challenging and is rarely incorporated in the planning process of an initiative. The current study examined 19 5-year plans developed during the planning phase of the Comprehensive Strategy for Serious, Violent and Chronic Juvenile Offenders. Quantitative and qualitative methods were employed to assess the extent to which the construct of sustainability was incorporated. The plan analysis was supplemented with results from other components of the complex evaluation design implemented as part of the process evaluation of Comprehensive Strategy. Results suggested that sustainability was not accounted for during the planning phase of this initiative. The implications of these findings, including the importance of planning for sustainability in order to achieve sustainability, are discussed.     

The changing practice of eating: evidence from UK time diaries, 1975 and 2000

This paper examines some central themes about change in consumption behaviour through an empirical investigation of the practice of eating. It analyses patterns of food consumption in the UK using time diary data from 1975 and 2000. The practice of eating is decomposed into four component activities which are used to explore systematically the inter-relationships between social processes - such as commodification and temporal fragmentation - and ways of providing and consuming food. It charts the expansion of eating out, the degree to which it substitutes for other eating activities, and the implications of its development for social relations and the temporal organization of daily life. Analysis reveals that food consumption continues to be differentiated along established lines of social division, although the content of those divisions has changed and varies across components of the practice. Increasing commodification of the food chain is documented, but without appearing to have a corrosive impact on household organization or social relationships. While tendencies indicative of temporal fragmentation are revealed, counter-tendencies exist which suggest that the practice of eating is resilient to many forms of external pressure. Finally, the application of a practice-based analytical approach permits critical evaluation of theories of social transformation.     

Assessing the Playing Field: A Prospective Longitudinal Study of Internet Sports Gambling Behavior

Internet gambling is growing rapidly, as is concern about its possible effect on the public’s health. This paper reports the results of the first prospective longitudinal study of actual Internet sports gambling behavior during eight study months. Data include recorded fixed-odds bets on the outcome of sporting contests and live-action bets on the outcome of events within contests for 40,499 Internet sports gambling service subscribers who enrolled during February 2005. We tracked the following primary gambling behaviors: daily totals of the number of bets made, money bet, and money won. We transformed these variables into measures of gambling involvement. We analyzed behavior for both fixed-odds and live-action bets. The median betting behavior of the 39,719 fixed-odds bettors was to place 2.5 bets of €4 (approximately $5.3 US) every fourth day during the median 4 months from first to last bet. This typical pattern incurred a loss of 29% of the amount wagered. The median betting behavior of the 24,794 live-action bettors was to place 2.8 wagers of €4 every fourth day during the median duration of 6 weeks at a loss of 18% of the amount wagered. We also examined the behavior of empirically determined groups of heavily involved bettors whose activity exceeded that of 99% of the sample.