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61.
闻斌 《常熟理工学院学报》2007,21(4):15-19
理论研究和实践结果表明,线性回归模型中最常用的方法——最小二乘法,在一些情况下表现不理想,因此近些年来,统计学家提出了许多替代方法供选择使用。本文通过参数经验Bayes(PEB)方法构造线性回归模型中可估函数的经验Bayes(EB)估计,并分别在均方误差(MSE)准则及均方误差矩阵(MSEM)准则下讨论它相对于最小二乘(LS)估计的优良性。 相似文献
62.
Heather A. Starnes Meghan H. McDonough Jeffrey S. Wilson Daniel K. Mroczek Francine Laden Philip J. Troped 《Measurement in physical education and exercise science》2019,23(2):135-147
The purpose of this study was to examine the factorial invariance of the Abbreviated Neighborhood Environment Walkability Scale (NEWS-A) across subgroups based on demographic, health-related, behavioral, and environmental characteristics among Nurses’ Health Study participants (N = 2,919; age M = 73.0, SD = 6.9 years) living in California, Massachusetts, and Pennsylvania. A series of multigroup confirmatory factor analyses were conducted to evaluate increasingly restrictive hypotheses of factorial invariance. Factorial invariance was supported across age, walking limitations, and neighborhood walking. Only partial scalar invariance was supported across state residence and neighborhood population density. This evidence provides support for using the NEWS-A with older women of different ages, who have different degrees of walking limitations, and who engage in different amounts of neighborhood walking. Partial scalar invariance suggests that researchers should be cautious when using the NEWS-A to compare older adults living in different states and neighborhoods with different levels of population density. 相似文献
63.
收益率的分布特征对于投资组合和风险管理理论具有重要意义.本文通过对上证指数进行全面系统研究,指出利用稳定分布能够更好地拟合我国股票市场的收益率,并且在稳定分布情况下,利用VaR和预期损失两个指标来度量风险. 相似文献
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65.
衡水湖国家级自然保护区湿地景观格局演变分析 总被引:9,自引:1,他引:9
基于1987年、1997年和2005年3期TM遥感数据,对衡水湖的湿地景观空间格局及其演变进行分析,结果表明:该区域以农田为景观基质,水体和芦苇沼泽交错分布构成区域湿地生境的主体斑块,其余景观类型呈以小尺度斑块散布于区域中。保护区湿地景观改变较明显,湿地由1987年的20.2%上升到1997年的23.4%,2005年占到22.3%,农田向湿地类型的转变最为显著,农田和湿地类型之间的动态转换关系很大程度上决定了保护区土地利用结构和景观格局的演变。从景观类型水平来看,表现为水体的平均斑块面积增加,由1987年的3.5187hm2减到1997年的2.0187hm2到2005年为4.3997hm2,破碎度指数下降;聚合度指数和最大斑块指数先降后升,而连接度指数先增后减;芦苇沼泽平均斑块面积下降明显,由1987年的2.6169hm2降到1997年的0.5437hm2,到2005年为0.3558hm2,且形状日趋复杂自然,最大斑块指数和聚合度指数持续减少,而连接度指数的变化趋势则相反,但总体上芦苇沼泽沼泽小面积斑块数量仍占相当比例,破碎化程度仍维持较高水平。在景观整体水平上,保护区的景观多样性和均匀度指数呈缓慢上升趋势,破碎化指数由1987年的51.068增到1997年的74.0985后2005年减为37.88,以农田为景观基质的蔓延度指数则先降后升。景观格局分析表明,衡水湖保护区湿地面积逐步恢复,破碎化程度降低且景观日趋多样化,连通性虽不及1987年历史最高水平却呈加强趋势,湿地生境质量得到优化,2005年湿地恢复的景观格局的空间配置达到3个时期的历史最高水平,也体现了保护区规划管理取得一定成效。 相似文献
66.
在分析Internet结构的基础上,主要针对BGP协议在AS级拓扑测量中的应用做了深入的讨论.介绍了自治系统的概念和BGP协议的工作过程,描述了监测运行有BGP协议路由器的路由表以动态构造AS级网络拓扑图的原理,给出了基于BGP协议的AS级网络拓扑测量的算法,并对算法进行了说明. 相似文献
67.
动作协调与"爆发力"表现田径跳跃动作协调能力测量与评价方法研究 总被引:2,自引:0,他引:2
通过专家访谈与问卷调查,确定了6组12项动作指标作为协调能力测试行为样本。运用生物力学方法与人体运动的动力学方法,以相同动作冗余自由度的控制与不控制作为刺激变量,以动作爆发力表现水平的差值为因变量,通过对两组不同水平被试测验成绩的比较,对跳跃专项动作协调能力进行了定性与定量评价。 相似文献
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69.
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
70.
Research on children’s physical self-concept (PSC) is increasingly recognised as an important field of psychology. However, there is a lack of instruments suitable for younger children at elementary school age. In the present study, a short German 21-item Physical Self-Concept-Questionnaire for children (PSCQ-C) was tested measuring seven specific facets of elementary school children’s PSC (strength, endurance, speed, flexibility, coordination, physical appearance, global sport competence). A number of 770 elementary school children aged 8–12 years completed the PSCQ-C. Results showed good psychometric properties and high reliabilities of the seven scales. Confirmatory factor analysis revealed that the presumed 7-factor model fitted the data best compared to a global 1- and 2-factor model. Also, full measurement invariance was strongly established. Correlations among the seven scales were mainly moderate. Gender differences were suggestive of developmental trends that are consistent with prior studies. These results provide support that the PSCQ-C is a confidential instrument with sound psychometric properties measuring seven specific facets of elementary school children’s PSC. 相似文献