Strategies for Efficient Experimental Design in Studies Probing 2-1-1 Mediation

Abstract

When well-implemented, mediation analyses play a critical role in probing theories of action because their results help lay the ground work for the critical development of a treatment and the iterative advancement of theories that are foundational to a discipline. Despite strong interest in designs that incorporate mediation, few studies have developed effective and efficient strategies to plan experiments examining multilevel mediation. We probe several design strategies for cluster-randomized designs and derive sampling plans that maximize power under cost constraints. The results suggest that among the more durable design strategies for mediation is covariance adjustment on variables predictive of the outcome and optimal sample allocation. The statistical power and optimal sample allocation results are implemented in the R package PowerUpR.     

Relationship between single digit addition strategies and working memory reflects general reasoning sophistication

With age, children employ increasingly more sophisticated strategies to solve single-digit addition (SDA) number fact problems. Changes in SDA strategy-use are correlated with age-related changes in cognitive measures (e.g., working-memory capacity, WM); however, this correlation does not explain the basis of SDA strategy-use or change per se. Does strategy-use reflect differences in generally reasoning abilities or are they uniquely tied to SDA abilities? Answers to these questions would help clarify the nature of SDA abilities specifically and early math abilities more generally. To investigate these issues, we assessed 144 5- to 9-year-olds' SDA strategies, visuospatial working memory (VSWM), verbal WM, non-verbal IQ, basic RT, and visuospatial reasoning abilities. We focused on these abilities since recent research shows visuospatial processes support early math development. We used latent profile/class analysis to classify children's SDA strategies and visuospatial reasoning abilities, which yielded four ability subgroups in both cases, only partially related to age. Findings show SDA strategy subgroup and general reasoning subgroup memberships were related. More sophisticated subgroups had better WM, but did not differ in IQ and RT. Findings suggest SDA reasoning reflect general reasoning abilities. Implications for math skills acquisition and intervention are discussed.     

对自然数9几个特殊运算性质的探讨

在人类历史,尤其是中国的历史上,自然数9被赋予了许多神秘的内涵.该文从自然数9与其它自然数运算的结果出发作进一步分析,推导出有关自然数9的三个定理及其五个推论,深入探讨9在四则运算中体现出的特殊性质,并对这些性质进行了初步的应用.     

基于音乐原理的电针仪的研究

本文在讨论音乐疗法机理的基础上,采用信号叠加原理,提出一种将音乐信号与电脉冲信号相结合的方法,在一定程度上解决了目前电针存在的适应性和耐受性问题。     

启智尺的研制与应用

根据珠算原理，我们研制了启智尺（组合数码尺），供儿童查数和计算加减法玩乐之用。最近，偶然发现此尺结合“素数表”可求解出“哥德巴赫猜想”。     

Addition and Subtraction of Three-digit Numbers: German Elementary Children's Success, Methods and Strategies

The present paper describes the success, the methods (mental, informal written, standard algorithm) and the strategies of informal written arithmetic to be observed when 300 elementary students worked on six addition and six subtraction problems with three-digit numbers. These twelve problems were administered repeatedly by means of a class test: in February (grade 3; nine-year-olds) before the standard algorithms were introduced, in June after they had been dealt with and in October at the beginning of grade 4. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bulk Polymerization of Styrene Using Benzyl Dithiobenzoate as a Chain Transfer

Bulk polymerization of styrene was carried out in the presence of a reversible addition-fragmentation chain transfer (RAFT) of benzyl dithiobenzoate (BDB). The comparison between reaction systems with and without BDB indicates that there is significant retardation in the reaction rate when BDB is used. The molecular weight of styrene polymer prepared with BDB shows linear relationship with the conversion of monomer, polydispersity is as narrow as 1.2, and no gel effects are observed during the polymerization with BDB, which are characteristics of a living radical polymerization. It has been found that the concentrations of BDB and azobis(isobutyronitrile) (AIBN) have opposite effects on the polymerization kinetics, and the AIBN dominates.     

论毛泽东农民思想的现实意义

农民问题是中国革命和建设的根本问题，也是毛泽东始终关注、系统调查、长期研究的问题。在长期的革命过程中，毛泽东结合中国实际形成了一整套关于农民问题的思想。这些宝贵的精神财富，对于建设现代农业，发展农村经济，增加农民收入，全面建设小康社会，具有重要的指导意义。     

灰色加法组合预测模型及其应用

针对季节性时间序列具有增长性和周期性的特点,将其进行分解建模,并与灰色系统理论相结合,首次提出了灰色加法组合预测模型。通过京津唐电网中的应用表明,此方法简单有效,对于季节性预测问题有很强的实用性和较高的预测精度。     

利用类比联想寻找和sum from k=1 to n(k~2)的方法

本文通过寻找求和 nk=1K2的方法,说明了类比、联想思维对解一个新问题的重要性,旨在启发学生解题时,要善于运用类比、联想,拓宽思路,激活思维,从而提高解题能力。