Effects of Missing Data Methods in SEM Under Conditions of Incomplete and Nonnormal Data

Using Monte Carlo simulations, this research examined the performance of four missing data methods in SEM under different multivariate distributional conditions. The effects of four independent variables (sample size, missing proportion, distribution shape, and factor loading magnitude) were investigated on six outcome variables: convergence rate, parameter estimate bias, MSE of parameter estimates, standard error coverage, model rejection rate, and model goodness of fit—RMSEA. A three-factor CFA model was used. Findings indicated that FIML outperformed the other methods in MCAR, and MI should be used to increase the plausibility of MAR. SRPI was not comparable to the other three methods in either MCAR or MAR.     

The Use of Multiple Imputation for Missing Data in Uniform DIF Analysis: Power and Type I Error Rates

Methods of uniform differential item functioning (DIF) detection have been extensively studied in the complete data case. However, less work has been done examining the performance of these methods when missing item responses are present. Research that has been done in this regard appears to indicate that treating missing item responses as incorrect can lead to inflated Type I error rates (false detection of DIF). The current study builds on this prior research by investigating the utility of multiple imputation methods for missing item responses, in conjunction with standard DIF detection techniques. Results of the study support the use of multiple imputation for dealing with missing item responses. The article concludes with a discussion of these results for multiple imputation in conjunction with other research findings supporting its use in the context of item parameter estimation with missing data.     

一维长程相互作用吸附模型的临界点与作用强度之间的Monte Carlo模拟研究

利用动力学Monte Carlo方法对一维长程相互作用吸附模型进行计算机模拟研究, 得出了其临界点λc与作用力程r-1-α中的α在α>1．0时具有指数关系:λc=λc0 Be-α/γ．     

双模压缩真空态的K次方H压缩效应

本文研究了双模压缩真空态1ξ〉=1/coshr sum from n=0 to(-e~(iθ)tanhr)~n 1n,n)的K次方H压缩效应。数值计算的结果表明:对于双模压缩真空态,光场存在着K次方H压缩效应(K=1,2,3,4,5,Λ);但是,随着方次K的升高,K次方H压缩效应减弱。     

Simulation Studies of the Effects of Small Sample Size and Studied Item Parameters on SIBTEST and Mantel-Haenszel Type I Error Performance

Two simulation studies investigated Type I error performance of two statistical procedures for detecting differential item functioning (DIF): SIBTEST and Mantel-Haenszel (MH). Because MH and SIBTEST are based on asymptotic distributions requiring "large" numbers of examinees, the first study examined Type 1 error for small sample sizes. No significant Type I error inflation occurred for either procedure. Because MH has the potential for Type I error inflation for non-Rasch models, the second study used a markedly non-Rasch test and systematically varied the shape and location of the studied item. When differences in distribution across examinee group of the measured ability were present, both procedures displayed inflated Type 1 error for certain items; MH displayed the greater inflation. Also, both procedures displayed statistically biased estimation of the zero DIF for certain items, though SIBTEST displayed much less than MH. When no latent distributional differences were present, both procedures performed satisfactorily under all conditions.     

The Power of the Test for Treatment Effects in Three-Level Cluster Randomized Designs

Abstract

Experiments that involve nested structures often assign entire groups (such as schools) to treatment conditions. Key aspects of the design of such experiments include knowledge of the intraclass correlation structure and the sample sizes necessary to achieve adequate power to detect the treatment effect. This study provides methods for computing power in three-level cluster randomized balanced designs (with two levels of nesting), where, for example, students are nested within classrooms and classrooms are nested within schools and schools are assigned to treatments. The power computations take into account nesting effects at the second (classroom) and at the third (school) level, sample size effects (e.g., number of schools, classrooms, and individuals), and covariate effects (e.g., pretreatment measures). The methods are applicable to quasi-experimental studies that examine group differences in an outcome.     

The Power of the Test for Treatment Effects in Three-Level Block Randomized Designs

Abstract

Experiments that involve nested structures may assign treatment conditions either to subgroups (such as classrooms) or individuals within subgroups (such as students). The design of such experiments requires knowledge of the intraclass correlation structure to compute the sample sizes necessary to achieve adequate power to detect the treatment effect. This study provides methods for computing power in three-level block randomized balanced designs (with two levels of nesting) where, for example, students are nested within classrooms and classrooms are nested within schools. The power computations take into account nesting effects at the second (classroom) and at the third (school) level, sample size effects (e.g., number of level-1, level-2, and level-3 units), and covariate effects (e.g., pretreatment measures). The methods are generalizable to quasi-experimental studies that examine group differences on an outcome.     

社会科学理论检验的复杂性与可错性

付检的社会科学理论的真假和实践的成功与否常常不对应,二者的关系极其复杂。分析检验过程的各个环节,就可发现导致检验复杂性、可错性的种种因素。只有对检验过程作全面深入的分析,才能得出正确的检验结论。     

IRT下题量与被试量对参数估计模拟返真性能的影响

在项目反应理论下的题库建设时,进行纸笔测验测试时需要多少被试量、题量,试题的参数估计能够达到较为精确估计?本文使用蒙特卡洛模拟方法模拟测验情境,对此问题进行探讨。分析题量的变化和被试量的变化对a、b参数估计的模拟返真性能的影响。1)从被试量角度来看,在两级、多级记分试题模拟测验情境下,随着被试量逐渐增大,项目参数估计值模拟返真指标均方误差逐渐减小。2)从题量角度来看,在两级记分试题模拟情境下,均方误差曲线在题量为25题左右时有一个拐点,即当题量小于25题时,随着题量增加时RMSE减小幅度较大,而当题量大于25题时,这时再增加题量,RMSE减小幅度很小。在多级记分试题模拟情境下,均方误差曲线在题量为15题左右时有一个拐点,即当题量小于15题时,随着题量增加, RMSE逐渐减小,当题量大于15题时,随着题量增加,RMSE逐渐增大。     

新型集成电源原理与应用

新型集成电源是—种性能先进,用途广泛的单片集成电路.本文分析了两种典型集成电源的工作原理,并对其应用技术做了详细介绍.     

全球化背景下的大国政治构建——以中国、俄罗斯、印度为例

在全球化背景下，建设大国已成为国际舞台上的重要景观。上世纪末本世纪初以来，中、俄、印三国都提出了建设大国的政治目标，进行了相应的政治建设。实践表明，要从国际政治战略的角度来认识国家的政治建设，大国建设不是全能政府的建设，而是要注重完善自身的文化构成。     

强权治下人格与意志的闪光--高文秀杂剧的时代精神与文化意蕴

高秀是元初声名卓的高产作家，他取材于历史和民间故事的三十多部杂剧，既融入了鲜明强烈的时代意识，彰显了独立不移、昂扬奋发的主体人格精神，也清晰地描出了元杂剧由金院本脱胎而来并逐步走向成熟的发展轨迹，具有浓郁醇厚的通俗化品味和值得珍视的戏曲史料价值。     

3G基站3KW风光发电互补型独立供电系统的设计

研究3G基站3KW风光发电互补型独立供电系统的结构设计与控制系统,系统基站备用储蓄电源,以充分保证基站在任何情况下都能正常供电。在不同天气状态下,实现风力发电和太阳能发电系互补。通过对不同天气和负载下的系统仿真实验,验证了3KW风光发电互补型独立供电系统的有效性。     

陕北地区普通话水平测试中常见声母、韵母错误类型分析

通过对若干不同等级应试测试语音材料的分析，归纳出陕北地区普通话水平测试中常见的声母错误36类，韵母错误51类，以期为测试员提供可供参考的语音评定参照框架。     

煤矿蓄电池电机车电源装置的运行与维护

结合开滦(集团)有限责任公司赵各庄矿业公司大量投入防爆特殊型蓄电池电机车的实际情况,研究了在蓄电池机车使用过程中,多功能环保电解液对蓄电池性能的影响,并提出了电源装置日常管理中应注意解决的主要问题,以便把握蓄电池管理运作的重点.