The Effect of Drop-Out on the Efficiency of Longitudinal Experiments

It is shown that drop-out often reduces the efficiency of longitudinal experiments considerably. In the framework of linear mixed models, a general, computationally simple method is provided, for designing longitudinal studies when drop-out is to be expected, such that there is little risk of large losses of efficiency due to the missing data. All the results are extensively illustrated using data from a randomized experiment with rats.     

Linearity of regression for non-adjacent record values

Let X₁,X₂,… be a sequence of iid random variables having a continuous distribution; by R₁,R₂,… denote the corresponding record values. All the distributions allowing linearity of regressions either E(R_m+k|R_m) or E(R_m|R_m+k) are identified.     

A theoretical analysis of the power of biased coin designs

Outlining some recently obtained results of Hu and Rosenberger [2003. Optimality, variability, power: evaluating response-adaptive randomization procedures for treatment comparisons. J. Amer. Statist. Assoc. 98, 671–678] and Chen [2006. The power of Efron's biased coin design. J. Statist. Plann. Inference 136, 1824–1835] on the relationship between sequential randomized designs and the power of the usual statistical procedures for testing the equivalence of two competing treatments, the aim of this paper is to provide theoretical proofs of the numerical results of Chen [2006. The power of Efron's biased coin design. J. Statist. Plann. Inference 136, 1824–1835]. Furthermore, we prove that the Adjustable Biased Coin Design [Baldi Antognini A., Giovagnoli, A., 2004. A new “biased coin design” for the sequential allocation of two treatments. J. Roy. Statist. Soc. Ser. C 53, 651–664] is uniformly more powerful than the other “coin” designs proposed in the literature for any sample size.     

Which Wald statistic? Choosing a parameterization of the Wald statistic to maximize power in k-sample generalized estimating equations

The Wald statistic is known to vary under reparameterization. This raises the question: which parameterization should be chosen, in order to optimize power of the Wald statistic? We specifically consider k-sample tests of generalized linear models (GLMs) and generalized estimating equations (GEEs) in which the alternative hypothesis contains only two parameters. An example is presented in which such an alternative hypothesis is of interest. Amongst a general class of parameterizations, we find the parameterization that maximizes power via analysis of the non-centrality parameter, and show how the effect on power of reparameterization depends on sampling design and the differences in variance across samples. There is no single parameterization with optimal power across all alternatives. The Wald statistic commonly used under the canonical parameterization is optimal in some instances but it performs very poorly in others. We demonstrate results by example and by simulation, and describe their implications for likelihood ratio statistics and score statistics. We conclude that due to poor power properties, the routine use of score statistics and Wald statistics under the canonical parameterization for GEEs is a questionable practice.     

PWM控制电路TC35C25及其应用

介绍了一种用于脉宽调制(PWM)控制器中的理想控制元件TC35C25.描述了该元件的构成,并就其在PWM控制电路中的应用进行了较详细的阐述.     

中国女排卫冕研究

中国女排近两年在世界大赛中取得了较好成绩,但与世界强队相比在进攻与拦网以及身体素质上还存在着明显差距,跳发球、后排进攻技术与立体进攻战术还不能熟练掌握和灵活运用．目前中国女排还不具备卫冕的实力．     

Locating “youth voice:” Considering the contexts of speaking in foster care

Within social services, an increasingly significant movement supports giving “voice” to children and youth, enabling them to express their views and to have those views taken into account in matters that affect them. In this article, the author draws from narratives of young people who grew up in foster care, examining stories of their efforts to impact the course of their own lives. The article explores the ways that very specific contexts and relationships of power shaped the utterances of young people in the foster care system and distorted, muted, or amplified their abilities to express their need and interests. This is a beginning attempt to identify ways that contexts of speaking in foster care can be understood and altered in order to strengthen the capacity of young people to voice their concerns and aspirations.     

The limits of the decentred state: the case of policing insurance claims fraud

Existing research clearly shows that the public–private divide is continuously being challenged, recast and transformed. However, this article argues that a sharp distinction between public and private continues to operate as an important norm for professionals involved in the investigation of insurance claims fraud in Sweden. It shows how power within private insurance companies and the police authority is organized around the public–private divide, which is in turn mobilized to justify repression and to give investigations legitimacy. The article indicates that the formal public–private distinction is far more thoroughly maintained than is suggested by the existing literature. Rather than challenging the centrality of state power, private insurers and the police construct, maintain and have a stake in the reproduction of a state‐centric monopoly of crime control.     

SPECULATORS AND TRAVELLERS THE POLITICAL CONSTRUCTION OF THE TOURIST IN THE KÁDÁR REGIME

This paper analyses the political construction of different types of tourists present in Hungary during the period of state socialism. After the 1956 revolution was crushed, Communist leadership sought to find new ways of legitimizing its power. One of the major legitimizing factors was raising standards of living. Another was the opening of the borders that is, allowing Hungarian citizens limited possibilities for travelling abroad. This concession was rather unique within the Communist Bloc, and it was not without its own dangers from the power holders' point of view. Citizens had to be guarded, controlled and supervized, not only to come back to Hungary,but also to think and feel properly in foreign countries. This paper demonstrates the efforts of the Communist Press, to bring into being construction of the ideal enlightened Tourist who is interested in art, museums and ‘social human values’. This ideal Tourist is set against with the Speculators, whose only concern is goods, especially Western goods, and have only ‘dirty’ material interest in travelling. This construction was doomed to fail due to a basic paradox: whereas the Kádár regime - quite successfully - stimulated consumer values in Hungary,one could hardly hope that these consumerist desires would be left behind during there vacation spent abroad.     

Resource characteristics in social exchange networks: Implications for positional advantage

Despite the wide range of resources that traverse social networks, social exchange research has focused on only a narrow subset. Notably, prior social exchange research has not considered resources like information that have the capacity to diffuse through networks. The current study investigates how differences between the standard social exchange resource and an information-type resource affect the advantage provided by one's network position. Results of a laboratory experiment support predictions and offer two new insights to the foundations of positional advantage: (1) the location of advantageous positions in a network differs by resource characteristics, and (2) only in particular situations is a single position able to experience high levels of both power and exchange frequency.