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1.
In this digital ITEMS module, Dr. Jeffrey Harring and Ms. Tessa Johnson introduce the linear mixed effects (LME) model as a flexible general framework for simultaneously modeling continuous repeated measures data with a scientifically defensible function that adequately summarizes both individual change as well as the average response. The module begins with a nontechnical overview of longitudinal data analyses drawing distinctions with cross-sectional analyses in terms of research questions to be addressed. Nuances of longitudinal designs, timing of measurements, and the real possibility of missing data are then discussed. The three interconnected components of the LME model—(1) a model for individual and mean response profiles, (2) a model to characterize the covariation among the time-specific residuals, and (3) a set of models that summarize the extent that individual coefficients vary—are discussed in the context of the set of activities comprising an analysis. Finally, they demonstrate how to estimate the linear mixed effects model within an open-source environment (R). The digital module contains sample R code, diagnostic quiz questions, hands-on activities in R, curated resources, and a glossary.  相似文献   
2.
1997-2000年江苏省成年人体质监测结果可比性分析与评价   总被引:4,自引:0,他引:4  
对 1997年和 2 0 0 0年本省 6万余例成年人按《标准》测试结果比较中的不合理现象的分析 ,表明在抽样、仪器和测试方法等环节存在影响纵向可比性的因素 ,并提出相应的建议  相似文献   
3.
包装层是对应于特定信息源的一种特殊程序,是实现异构信息源集成的关键。数字图书馆的包装层可以作为数字图书馆的智能前端代理,负责把来自中介层的统一查询表示映射为针对具体数字图书馆的查询格式,并从得到的查询结果中提取出用户需要的信息,提交给中介层。数字图书馆包装层生成的关键技术主要有:查询映射机制,查询服务调用机制,结果提取与转换机制。图6。参考文献5。  相似文献   
4.
ABSTRACT

Participation in youth sport is positively associated with physical fitness and performance. The purpose of the current study was to examine if physical fitness measures during childhood and early adolescence predicted high school sport participation. Participants included youth in the Michigan State University Motor Performance Study. Measures consisted of the endurance shuttle run, Wells sit-and-reach, jump and reach, standing long jump, agility shuttle run and 30-yard dash. Individual, generalized estimating equation models were used to estimate the association between each measure and the odds of participating in high school sport. For both sexes, the endurance shuttle run and agility shuttle run were related to sport participation. For boys only, the long jump and 30-yard dash were also associated with sport participation. Better physical fitness and performance across several dimensions in childhood, including those related to motor skills, enhanced the likelihood of sport participation in high school.  相似文献   
5.
In facilitating the adoption of exercise behavior, attention should be directed towards the dynamic nature of behavioral regulations. Organismic integration theory presents a suitable framework for investigating fluctuations in behavioral regulations. However, current results pertaining to this issue revealed mixed findings. The aim of this review is to examine the empirical literature on the dynamic nature of organismic integration theory in exercise settings over time in adults. A systematic review of English articles using PsycINFO, PsycARTICLES, ScienceDirect, and SPORTDiscus was conducted including keywords of organismic integration theory, longitudinal designs, change in behavioral regulations, and exercise. Findings are summarized through quantitative analysis of the evidence. Regarding autonomous regulations, steady increases in regulations are observable that originate within the first weeks and persist for up to one year. Most studies reported no changes in controlled regulations, although in a few cases changes were observed six weeks after baseline or later. The review adds to the theoretical understanding of how behavioral regulations are internalized. However, whether changes in regulation occur depends on both the type of regulation and on contextual characteristics. Future research of longitudinal design is warranted to identify optimal periods in which individuals seek for increased support during exercise adoption.  相似文献   
6.
二次域上的理想类数是有限的,文章利用理想类、类群的相关性质,通过计算机编程,求解出二次域Z(D)的类数及理想的代表。  相似文献   
7.
Multi-domain and longitudinal studies of student achievement routinely find moderate to strong correlations across achievement domains and even stronger within-domain correlations over time. The purpose of this study is to examine the sources of these patterns analysing student achievement in 5 domains across Years 3, 5 and 7. The analysis is of longitudinal population data of over 22,000 students and utilizes fixed-effects models to incorporate stable general and domain-specific latent factors. These latent factors correspond to a general cognitive-ability-like factor and specific aptitudes in particular, or types of, subject areas. The preferred model incorporates both general and domain-specific latent factors with stronger effects for the general factor, although the domain-specific factors are particularly strong for spelling and numeracy. When taking into account general and domain-specific latent factors, the effects of student’s socioeconomic status (SES) and school SES are trivial.  相似文献   
8.
随机数是蒙特卡罗(Monte Carlo)方法的关键因素.首先给出一种广义反馈位移寄存器发生器及其缺点,然后在此基础上提出一种基于两个广义反馈位移寄存器方法的组合随机数发生器,最后给出一些严密的统计检验,结果证明这种组合随机数发生器不失为一种较好的随机数发生器.  相似文献   
9.
This paper argues that teachers' recognition of children's cultural practices is an important positive step in helping socio‐economically disadvantaged children engage with school literacies. Based on 21 longitudinal case studies of children's literacy development over a 3‐year period, the authors demonstrate that when children's knowledges and practices assembled in home and community spheres are treated as valuable material for school learning, children are more likely to invest in the work of acquiring school literacies. However, they also show that while some children benefit greatly from being allowed to draw on their knowledge of popular culture, sports and the outdoors, other children's interests may be ignored or excluded. Some differences in teachers' valuing of home and community cultures appeared to relate to gender dimensions.  相似文献   
10.
Models to assess mediation in the pretest–posttest control group design are understudied in the behavioral sciences even though it is the design of choice for evaluating experimental manipulations. The article provides analytical comparisons of the four most commonly used models to estimate the mediated effect in this design: analysis of covariance (ANCOVA), difference score, residualized change score, and cross-sectional model. Each of these models is fitted using a latent change score specification and a simulation study assessed bias, Type I error, power, and confidence interval coverage of the four models. All but the ANCOVA model make stringent assumptions about the stability and cross-lagged relations of the mediator and outcome that might not be plausible in real-world applications. When these assumptions do not hold, Type I error and statistical power results suggest that only the ANCOVA model has good performance. The four models are applied to an empirical example.  相似文献   
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