On Sample-Size Calculations for Precise Contrast Analysis in ANCOVA     

Gwowen Shieh 《Journal of Experimental Education》2019,87(2):238-259

The analysis of covariance (ANCOVA) is a useful statistical procedure that incorporates covariate features into the adjustment of treatment effects. The consequences of omitted prognostic covariates on the statistical inferences of ANCOVA are well documented in the literature. However, the corresponding influence on sample-size calculations for precise interval estimation has not been fully evaluated. This article aims to explicate the deficiency of approximate methods for ignoring the stochastic nature of covariate variables and to present exact approaches for precise interval estimation of treatment contrasts under the assumption that the covariate variables have a joint multinormal distribution. The desired precision of a confidence interval is assessed with respect to the control of expected half-width and to the assurance probability of interval half-width within a designated value. Numerical appraisals show that the suggested approaches outperform the approximate formulas for the two precision considerations.  相似文献   

商务英语写作修辞意识的构建及其培养方法     

李太志 《茂名学院学报》2011,21(5):26-28

商务英语写作修辞意识的框架系统包含几十种成对的语言表达手段、写作修辞方法、写作修辞现象以及它们体现的写作修辞原则和倾向。在教学中,培养商务英语写作修辞意识的具体方法主要有二：通过实例对比分析树立明确的商务英语写作修辞意识;通过写作训练建立商务英语写作修辞意识,写作训练的具体训练法有修改提高法和完形选择法。  相似文献   

Rapid phenotypic evolution with shallow genomic differentiation during early stages of high elevation adaptation in Eurasian Tree Sparrows     

Yanhua Qu  Chunhai Chen  Ying Xiong  Huishang She  Yong E Zhang  Yalin Cheng  Shane DuBay  Dongming Li  Per G P Ericson  Yan Hao  Hongyuan Wang  Hongfeng Zhao  Gang Song  Hailin Zhang  Ting Yang  Chi Zhang  Liping Liang  Tianyu Wu  Jinyang Zhao  Qiang Gao  Weiwei Zhai  Fumin Lei 《国家科学评论(英文版)》2020,7(1):113

Known as the ‘third polar region’, the Qinghai-Tibet Plateau represents one of the harshest highland environments in the world and yet a number of organisms thrive there. Previous studies of birds, animals and humans have focused on well-differentiated populations in later stages of phenotypic divergence. The adaptive processes during the initial phase of highland adaptation remain poorly understood. We studied a human commensal, the Eurasian Tree Sparrow, which has followed human agriculture to the Qinghai-Tibet Plateau. Despite strong phenotypic differentiation at multiple levels, in particular in muscle-related phenotypes, highland and lowland populations show shallow genomic divergence and the colonization event occurred within the past few thousand years. In a one-month acclimation experiment investigating phenotypic plasticity, we exposed adult lowland tree sparrows to a hypoxic environment and did not observe muscle changes. Through population genetic analyses, we identified a signature of polygenic adaptation, whereby shifts in allele frequencies are spread across multiple loci, many of which are associated with muscle-related processes. Our results reveal a case of positive selection in which polygenic adaptation appears to drive rapid phenotypic evolution, shedding light on early stages of adaptive evolution to a novel environment.  相似文献   

The dynamic control ratio at the equilibrium point (DCRe): introducing relative and absolute reliability scores     

Tobias Alt  Axel J. Knicker  Heiko K. Strüder 《Journal of sports sciences》2017,35(7):688-693

Analytical methods to assess thigh muscle balance need to provide reliable data to allow meaningful interpretation. However, reproducibility of the dynamic control ratio at the equilibrium point has not been evaluated yet. Therefore, the aim of this study was to compare relative and absolute reliability indices of its angle and moment values with conventional and functional hamstring–quadriceps ratios. Furthermore, effects of familiarisation and angular velocity on reproducibility were analysed. A number of 33 male volunteers participated in 3 identical test sessions. Peak moments (PMs) were determined unilaterally during maximum concentric and eccentric knee flexion (prone) and extension (supine position) at 0.53, 1.57 and 2.62 rad · s^–1. A repeated measure, ANOVA, confirmed systematic bias. Intra-class correlation coefficients and standard errors of measurement indicated relative and absolute reliability. Correlation coefficients were averaged over respective factors and tested for significant differences. All balance scores showed comparable low-to-moderate relative (<0.8–0.9) and good absolute reliability (<10%). Relative reproducibility of dynamic control equilibrium parameters augmented with increasing angular velocity, but not with familiarisation. At 2.62 rad · s^–1, high (moment: 0.906) to moderate (angle: 0.833) relative reliability scores with accordingly high absolute indices (4.9% and 6.4%) became apparent. Thus, the dynamic control equilibrium is an equivalent method for the reliable assessment of thigh muscle balance.  相似文献   

起跳过程送髋技术对跳远的影响     

武文杰 《湖北体育科技》2010,(3)

研究目的:跳远起跳过程中髋关节技术特征是跳远动作中最为重要的部分,对提高与改进跳远起跳技术有着重要的影响,掌握在跳远的起跳、着板、缓冲、蹬伸阶段"送髋"的角度和方法,为提高我国跳远水平提供具体量化参考指标。研究方法:根据我国运动员调控髋关节运动的状况和国内与国外优秀运动员跳高的差距,通过对比研究起跳过程中髋关节技术特征。研究结果和结论:跳远运动必须合理地完善起跳技术动作,在训练中专门发展髋关节肌肉的力量,以及髋关节灵活性,有意识地运用髋关节动作协调非常重要。  相似文献   

负重训练和补充大豆多肽干预大鼠骨骼肌衰老过程的实验研究     

刘丰彬  赵斌  闫万军  马炳存 《天津体育学院学报》2010,25(1):33-37

目的:探讨负重训练和补充大豆多肽干预大鼠骨骼肌衰老过程的作用效果.方法:56只雄性SD大鼠随机分为7组:成年组,模型组,D-半乳糖小负重组,D-半乳糖大负重组,D-半乳糖补肽组,D-半乳糖补肽小负重组,D-半乳糖补肽大负重组.6周后处死大鼠,制作冰冻切片,测试血清以及骨骼肌各项指标.结果:与成年组相比,模型组大鼠体重和每日摄食量分别呈现升高和下降的趋势,负重和补肽可以在一定程度上缓解两种趋势,但都无统计学意义;模型组大鼠骨骼肌细胞出现萎缩和退行性改变等衰老的迹象,负重和补肽可以在一定程度上减轻这种现象;模型组大鼠血清SOD、SOD/MDA比值和骨骼肌总蛋白含量显著低于成年组,血清MDA显著高于成年组,运动和营养干预各组显著逆转这种趋势,并有明显的交互作用;与成年组相比,模型组大鼠骨骼肌脂褐素含量显著升高,负重或补肽可以一定程度上缓解或逆转这种趋势,两种具有明显的交互作用.结论:负重训练或补充大豆多肽均可以有效的预防大鼠骨骼肌衰老过早的出现,两种方式联合运用效果更为明显.  相似文献   

科技期刊中英文摘要体裁对比与分析   总被引：1，自引：1，他引：1  

李平  牟爱鹏 《编辑学报》2005,17(6):425-427

运用体裁分析理论对中英文摘要的体裁结构进行对比分析.首先是摘要结构的宏观对比,然后是基本要素的逐项对比.结果表明,中英文摘要的宏观结构和各个要素的组织模式有很大的相似性,但是也存在着较大的差异.英文摘要的结构较之中文摘要更加完整.  相似文献   

投掷运动员体成分的调查分析   总被引：1，自引：0，他引：1  

吕新颖 《北京体育大学学报》1999,(3)

通过对受试者体成分皮褶厚度的测定,并对其派生指标的比较发现：投掷选手皮脂较厚,其中重器械投掷选手达到肥胖标准。分析认为,这是由于其肌肉体积逐渐增大的同时,总伴随着皮下脂肪逐渐堆积的结果。肥胖不仅影响运动的效果,对身体健康也不利。建议投掷选手在促使肌肉体积增大的同时应积极采取消除脂肪的措施。  相似文献   

跨栏技术的运动解剖学分析     

潘春梅  金丽颖 《山西师大体育学院学报》1995,(1)

跨栏运动员在提高短跑速度的同时,如何改进跨栏技术?本文针对摆动腿、起跨腿、摆臂三方面的问题,从运动解剖学角度进行分析,提出加强后蹬肌群、肩带肌群和盆带肌群在力量、柔韧性和灵活性等方面的训练,从而提高全身动作的协调性,促进跨栏技术的提高。  相似文献   

电子期刊评价体系构建     

周婷婷  徐宽 《图书馆学研究》2007,(10):97-100,F0003

本文综合考虑数据库的各种因素来评价电子期刊资源，包括学科范围、核心期刊指数、检索功能、价格等，从定性和定量两方面对电子期刊进行综合评价，探索性地建立了比较评价指标体系。  相似文献