共查询到20条相似文献，搜索用时 797 毫秒
1.
Equating methods make use of an appropriate transformation function to map the scores of one test form into the scale of another so that scores are comparable and can be used interchangeably. The equating literature shows that the ways of judging the success of an equating (i.e., the score transformation) might differ depending on the adopted framework. Rather than targeting different parts of the equating process and aiming to evaluate the process from different aspects, this article views the equating transformation as a standard statistical estimator and discusses how this estimator should be assessed in an equating framework. For the kernel equating framework, a numerical illustration shows the potentials of viewing the equating transformation as a statistical estimator as opposed to assessing it using equating‐specific criteria. A discussion on how this approach can be used to compare other equating estimators from different frameworks is also included. 相似文献
2.
关于函数的一致连续性 总被引：2，自引：0，他引：2
葛洵 《商丘师范学院学报》2003,19(5):57-58
R的子集D称为具有性质L，如果任一覆盖D的开区间族有Lebesgue数。证明了如果R的子集D具有性质L，则定义在D上的连续函数是一致连续的。作为上述结果的一个推论，改进了通常关于函数一致连续性的一个结果，得到了R的紧致子集(闭区间)上的连续函数是一致连续的。 相似文献
3.
胡舒合 《韩山师范学院学报》2003,24(3):13-15
研究了独立或相依样本时非参数回归函数的Nadaraya-Watson估计，在简洁合理的条件下，证明了估计量的渐近正态性，获得的结论可在时间序列分析中得到应用． 相似文献
4.
Daniel F. McCaffrey Katherine E. Castellano J. R. Lockwood 《Educational Measurement》2015,34(1):15-21
Student growth percentiles (SGPs) express students' current observed scores as percentile ranks in the distribution of scores among students with the same prior‐year scores. A common concern about SGPs at the student level, and mean or median SGPs (MGPs) at the aggregate level, is potential bias due to test measurement error (ME). Shang, vanIwaarden, and Betebenner (SVB; this issue) develop a simulation‐extrapolation (SIMEX) approach to adjust SGPs for test ME. In this paper, we use a tractable example in which different SGP estimators, including SVB's SIMEX estimator, can be computed analytically to explain why ME is detrimental to both student‐level and aggregate‐level SGP estimation. A comparison of the alternative SGP estimators to the standard approach demonstrates the common bias‐variance tradeoff problem: estimators that decrease the bias relative to the standard SGP estimator increase variance, and vice versa. Even the most accurate estimator for individual student SGP has large errors of roughly 19 percentile points on average for realistic settings. Those estimators that reduce bias may suffice at the aggregate level but no single estimator is optimal for meeting the dual goals of student‐ and aggregate level inferences. 相似文献
5.
非参数核密度估计具有良好的性质,有固定窗宽和变窗宽两种形式,由于渐近方差收敛率相同,而渐近偏度存在差异,固定窗宽和球估计量的偏度为h2,Ambramson估计量为h4,本文提出了固定窗宽核密度估计量的一个性质,并计算基于均匀核的柯西密度Ambramson估计量的期望发现刚好是无偏的。 相似文献
6.
本文讨论了线性模型当随机误差为位置分布族时参数的同变估计,并给出了最优同变估计(MREE),结果表明线性模型参数的最优同变估计与最小二乘估计是一致的. 相似文献
7.
Psychometric properties of item response theory proficiency estimates are considered in this paper. Proficiency estimators based on summed scores and pattern scores include non-Bayes maximum likelihood and test characteristic curve estimators and Bayesian estimators. The psychometric properties investigated include reliability, conditional standard errors of measurement, and score distributions. Four real-data examples include (a) effects of choice of estimator on score distributions and percent proficient, (b) effects of the prior distribution on score distributions and percent proficient, (c) effects of test length on score distributions and percent proficient, and (d) effects of proficiency estimator on growth-related statistics for a vertical scale. The examples illustrate that the choice of estimator influences score distributions and the assignment of examinee to proficiency levels. In particular, for the examples studied, the choice of Bayes versus non-Bayes estimators had a more serious practical effect than the choice of summed versus pattern scoring. 相似文献
8.
本文基于模糊变量的可信性分布,提出了模糊极大似然估计的概念,证明了模糊极大似然估计的不变性及其收敛性。 相似文献
9.
INTRODUCTION The technology of smart or adaptive antennawhich can increase capacity and range, and reducesmultipath propagation of mobile radio communi-cation system, has aroused great interest in recentyears (Haardt and Spencer, 2003; Bellofiore, 2002;Godara, 1997). Beamforming is a key technologyin smart antenna systems (SAS) and many differentadaptive beamforming algorithms have been pro-posed. Code division multiple access (CDMA)system will be applied in most mobile communi-… 相似文献
10.
马海珠 《浙江教育学院学报》2005,(5):46-52
利用旋转异构态模型和伪立体化学平衡统计方法,得到考虑侧基的均方回转半径及温度系数的改进公式,研究典型的大侧基聚衣康酸酯链的构象和构型性质.并通过数值计算,研究无规聚衣康酸酯链均方回转半径特征比、温度系数与构象能的关系,研究链规整程度对均方回转半径特征比的影响. 相似文献
11.
本文引进矩阵的正交不变范数,定义出矩阵估计量的优良性准则,在通常的容许性意义下,得到了带有线性约束的共同均值矩阵的线性估计是泛可容许的充要条件,进而得到了在不同的线性约束条件下,的泛可容许估计类之间的一种刻划。 相似文献
12.
史建红 《吕梁高等专科学校学报》1999,15(4):22-26
本文提出了约束线性模型下回归系统的条件根方估计和广义条件根方估计,证明了在一定的条件下,两者在均方误差意义都能很好地改进回归系数的约束最小二乘估计,并讨论了它们的可容许性及广义条件根方估计中未知参数的选取方法。 相似文献
13.
讨论了Choquet积分定义的单调集函数的几个遗传性质．证明了Choquet积分定义的新的单调集函数遗传了原来集函数的几个重要的结构特性，如弱零可加性、强序连续性、性质(S)和伪距离生成性质等．最后通过2个例子说明了当被积函数不是C可积时，强序连续性和伪距离生成性质将不再被保留． 相似文献
14.
考虑纵向数据半参数回归模型:Y=Xβ+g(T)+ε,基于最小二乘法和局部线性拟合的方法建立了模型中参数分量β,回归函数g(·)和误差方差σ2的估计量,并在适当条件下得到了它们的渐近正态性和最优收敛速度. 相似文献
15.
Three optimal linear attitude estimators are proposed for single-point real-time estimation of spacecraft attitude using a
geometric approach. The final optimal attitude is represented by modified Rodrigues parameters (MRPs). After introducing incidental
right-hand orthogonal coordinates for each pair of measured values, three error vectors are obtained by the use of dot or/and
cross products. Corresponding optimality criteria are rigorously quadratic and unconstrained, which do not coincide with Wahba’s
constrained criterion. The singularity, which occurs when the principal angle is close to π, can be easily avoided by one
proper rotation. Numerical simulations show that the proposed three optimal linear estimators can provide a precision comparable
with those complying with the Wahba optimality definition, and have faster computational speed than the famous quaternion
estimator (QUEST). 相似文献
16.
导函数的特殊性质 总被引：2，自引：0，他引：2
朱文辉 《南通职业大学学报》2003,17(3):64-66
章讨论了导数的连续性，得到了导函数有极限必连续以及导数值存在时导函数间断必振荡等结论。章研究了导函数的介值性，发现介值性不需要有连续的前提，同时指出了导函数振荡间断回归性的更深刻内涵。 相似文献
18.
19.
20.
在逐步Ⅱ型截尾样本下讨论了逆Rayleigh分布参数的估计问题,给出了参数的最大似然估计,并在三种不同的损失函数下给出了参数的Bayes估计和区间估计.最后给出了数值模拟的例子。 相似文献