共查询到20条相似文献，搜索用时 15 毫秒
1.
One challenge in mediation analysis is to generate a confidence interval (CI) with high coverage and power that maintains a nominal significance level for any well-defined function of indirect and direct effects in the general context of structural equation modeling (SEM). This study discusses a proposed Monte Carlo extension that finds the CIs for any well-defined function of the coefficients of SEM such as the product of k coefficients and the ratio of the contrasts of indirect effects, using the Monte Carlo method. Finally, we conduct a small-scale simulation study to compare CIs produced by the Monte Carlo, nonparametric bootstrap, and asymptotic-delta methods. Based on our simulation study, we recommend researchers use the Monte Carlo method to test a complex function of indirect effects. 相似文献
2.
Early childhood classrooms support children's learning in a variety of ways. Of critical importance are the interactions teachers have with children. The type and quality of classroom interactions vary and can be grouped into three domains: instructional, organizational, and emotional. The purpose of this study is to examine the extent to which the quality of classroom interactions is stable over time and the extent to which certain types of interactions (e.g., organizational) set the stage for other types of interactions (e.g., instructional) during the first two hours of a typical pre-k day. Classrooms (n = 693) were observed during four contiguous observation cycles (20 min for observation, 10 min for ratings) using the Classroom Assessment Scoring System. Stability estimates from autoregressive models showed the quality of classroom interactions was highly stable. Latent difference score models were then fit to determine how these domains of teacher interactions related with one another over time. Contrary to hypotheses, higher levels of Classroom Organization and Emotional Support were not related to positive changes in Instructional Support. However, the final model indicated that Classroom Organization and Emotional Support were positively related to one another over time. That is, higher levels of Classroom Organization were related to higher levels of Emotional Support at the next observation cycle and vice versa. Implications for the understanding of classroom interactions and the measurement of interactions are discussed. 相似文献
3.
Kevin J. Grimm Yang An John J. McArdle Alan B. Zonderman Susan M. Resnick 《Structural equation modeling》2013,20(2):268-292
Latent difference score models (e.g., McArdle & Hamagami, 2001) are extended to include effects from prior changes to subsequent changes. This extension of latent difference scores allows for testing hypotheses where recent changes, as opposed to recent levels, are a primary predictor of subsequent changes. These models are applied to bivariate longitudinal data collected as part of the Baltimore Longitudinal Study of Aging on memory performance, measured by the California Verbal Learning Test, and lateral ventricle size, measured by structural MRIs. Results indicate that recent increases in the lateral ventricle size were a leading indicator of subsequent declines in memory performance from age 60 to 90. 相似文献
4.
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
5.
When multiple raters score a writing sample, on occasion they will award discrepant scores. To report a single score to the examinee, some method of resolving those differences must be applied to the ratings before an operational score can be reported. Several forms of resolving score discrepancies have been described in the literature. Initial studies of the various methods, however, have demonstrated that decisions about student performance may differ depending on the resolution method applied. Thus, studies are needed to investigate the quality of the scores associated with each model. To study score quality associated with each model, we conducted a Monte Carlo study and varied the factors associated with scoring and resolution to determine the conditions under which a particular resolution method might be superior. 相似文献
6.
The purpose of this study was to explore the influence of the number of targets specified on the quality of exploratory factor analysis solutions with a complex underlying structure and incomplete substantive measurement theory. Three Monte Carlo studies were performed based on the ratio of the number of observed variables to the number of underlying factors. Within each study, communality, sample size, and the number of targets were manipulated. Outcomes included a measure of congruence and a measure of variability with regard to the rotated pattern matrix. The magnitude of the main effect for the influence of the number of targets on congruence and variability ranged from moderate to large. The magnitude of the interaction between the number of targets and level of communality ranged from small to moderate with regard to congruence and variability. Consistent with theoretical expectations, the minimum number of targets to specify to be reasonably assured of obtaining an accurate solution varied across study conditions. 相似文献
7.
Daniel McNeish 《Structural equation modeling》2017,24(4):609-625
Multilevel structural equation modeling (ML-SEM) for multilevel mediation is noted for its flexibility over a system of multilevel models (MLMs). Sample size requirements are an overlooked limitation of ML-SEM (100 clusters is recommended). We find that 89% of ML-SEM studies have fewer than 100 clusters and the median number is 44. Furthermore, 75% of ML-SEM studies implement 2–1–1 or 1–1–1 models, which can be equivalently fit with MLMs. MLMs theoretically have lower sample size requirements, although studies have yet to assess small sample performance for multilevel mediation. We conduct a simulation to address this pervasive problem. We find that MLMs have more desirable small sample performance and can be trustworthy with 10 clusters. Importantly, many studies lack the sample size and model complexity to necessitate ML-SEM. Although ML-SEM is undeniably more flexible and uniquely positioned for difficult problems, small samples often can be more effectively and simply addressed with MLMs. 相似文献
8.
Carla Gerhard Andreas G. Klein Karin Schermelleh-Engel Helfried Moosbrugger Jana Gäde Holger Brandt 《Structural equation modeling》2013,20(2):276-287
This article investigates likelihood-based difference statistics for testing nonlinear effects in structural equation modeling using the latent moderated structural equations (LMS) approach. In addition to the standard difference statistic TD, 2 robust statistics have been developed in the literature to ensure valid results under the conditions of nonnormality or small sample sizes: the robust TDR and the “strictly positive” TDRP. These robust statistics have not been examined in combination with LMS yet. In 2 Monte Carlo studies we investigate the performance of these methods for testing quadratic or interaction effects subject to different sources of nonnormality, nonnormality due to the nonlinear terms, and nonnormality due to the distribution of the predictor variables. The results indicate that TD is preferable to both TDR and TDRP. Under the condition of strong nonlinear effects and nonnormal predictors, TDR often produced negative differences and TDRP showed no desirable power. 相似文献
9.
Mediation is one concept that has shaped numerous theories. The list of problems associated with mediation models, however, has been growing. Mediation models based on cross-sectional data can produce unexpected estimates, so much so that making longitudinal or causal inferences is inadvisable. Even longitudinal mediation models have faults, as parameter estimates produced by these models are specific to the lag between observations, leading to much debate over appropriate lag selection. Using continuous time models (CTMs) rather than commonly employed discrete time models, one can estimate lag-independent parameters. We demonstrate methodology that allows for continuous time mediation analyses, with attention to concepts such as indirect and direct effects, partial mediation, the effect of lag, and the lags at which relations become maximal. A simulation compares common longitudinal mediation methods with CTMs. Reanalysis of a published covariance matrix demonstrates that CTMs can be fit to data used in longitudinal mediation studies. 相似文献
10.
Dynamic structural equation modeling (DSEM) is a novel, intensive longitudinal data (ILD) analysis framework. DSEM models intraindividual changes over time on Level 1 and allows the parameters of these processes to vary across individuals on Level 2 using random effects. DSEM merges time series, structural equation, multilevel, and time-varying effects models. Despite the well-known properties of these analysis areas by themselves, it is unclear how their sample size requirements and recommendations transfer to the DSEM framework. This article presents the results of a simulation study that examines the estimation quality of univariate 2-level autoregressive models of order 1, AR(1), using Bayesian analysis in Mplus Version 8. Three features are varied in the simulations: complexity of the model, number of subjects, and number of time points per subject. Samples with many subjects and few time points are shown to perform substantially better than samples with few subjects and many time points. 相似文献
11.
This article presents several longitudinal mediation models in the framework of latent growth curve modeling and provides a detailed account of how such models can be constructed. Logical and statistical challenges that might arise when such analyses are conducted are also discussed. Specifically, we discuss how the initial status (intercept) and change (slope) of the putative mediator variable can be appropriately included in the causal chain between the independent and dependent variables in longitudinal mediation models. We further address whether the slope of the dependent variable should be controlled for the dependent variable's intercept to improve the conceptual relevance of the mediation models. The models proposed are illustrated by analyzing a longitudinal data set. We conclude that for certain research questions in developmental science, a multiple mediation model where the dependent variable's slope is controlled for its intercept can be considered an adequate analytical model. However, such models also show several limitations. 相似文献
12.
The aim of this study was to understand and characterize the adsorption of small alkanes, namely methane, ethane and propane, in zeolite TON through detailed Monte Carlo simulations. The isotherms of pure components were calculated and showed good agreement with experimental data. The adsorption positions, adsorption energy of pure components and isotherms of mixtures were also simulated and the results are discussed. 相似文献
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14.
To overcome the excessive computational cost and/or bad accuracy of traditional approaches,the probabilistic density evolution method(PDEM) is introduced.The dynamic reliability of a double-layer cylindrical latticed shell is evaluated by applying PDEM and Monte Carlo Method(MCM) respectively,and four apparent wave velocities(100 m/s,500 m/s,800 m/s and 1 200 m/s) and five thresholds(0.1 m,0.2 m,0.3 m,0.4 m and 0.5 m) are taken into consideration.Only the difference between threshold and maximal deformation... 相似文献
15.
The relation between 2 forms of mathematical cognition, calculations and word problems, was examined. Across grades 2–3, performance of 328 children (mean starting age 7.63 [SD = 0.43]) was assessed 3 times. Comparison of a priori latent change score models indicated a dual change model, with consistently positive but slowing growth, described development in each domain better than a constant or proportional change model. The bivariate model including change models for both calculations and word problems indicated prior calculation performance and change were not predictors of subsequent word-problem change, and prior word-problem performance and change were not predictors of subsequent calculation change. Results were comparable for boys versus girls. The bivariate model, along with correlations among intercepts and slopes, suggest calculation and word-problem development are related, but through an external set of overlapping factors. Exploratory supplemental analyses corroborate findings and provide direction for future study. 相似文献
16.
In latent growth modeling, measurement invariance across groups has received little attention. Considering that a group difference is commonly of interest in social science, a Monte Carlo study explored the performance of multigroup second-order latent growth modeling (MSLGM) in testing measurement invariance. True positive and false positive rates in detecting noninvariance across groups in addition to bias estimates of major MSLGM parameters were investigated. Simulation results support the suitability of MSLGM for measurement invariance testing when either forward or iterative likelihood ratio procedure is applied. 相似文献
17.
刘爱云 《信阳师范学院学报(哲学社会科学版)》2001,21(3):42-45
有关教育和个体教育的论述,多离不开人的潜能问题。对人的潜能,人本主义进行了比较多的论述,但其论述仅停留于对潜能同一性的认识,事实上,潜能的差异性不仅构成了个体最初不同的内部状态,而且在人的一生中都持续地发挥着作用,个体就是在这种差异潜能和环境的交互作用中发展起来的。这种交互作用使个体发展和社会发展构成了交互影响的统一体,这一点应引起我们教育和管理工作的高度重视。 相似文献
18.
测验分数由于受到评分者和测验难度的影响,因而不能很好地评价学生的学业状况.能力分数仅与被试有关,与测验的难度无关.能力分数的特征有:能力分数是相合估计,能力分数是"不变分数",能力分数呈正态分布.在能力分数的意义下,对于来自不同测验的能力分数可以直接进行对比. 相似文献
19.
雷桂媛 《浙江大学学报(A卷英文版)》2002,3(3):339-343
The rejection sampling method is one of the most popular methods used in Monte Carlo methods. It turns out that the standard rejection method is closely related to the problem of quasi-Monte Carlo integration of characteristic functions, whose accuracy may be lost due to the discontinuity of the characteristic functions. We proposed a B-splines smoothed rejection sampling method, which smoothed the characteristic function by B-splines smoothing technique without changing the integral quantity. Numerical experiments showed that the convergence rate of nearly O(N-1) is regained by using the B-splines smoothed rejection method in importance sampling. 相似文献
20.
Statistical theories of goodness-of-fit tests in structural equation modeling are based on asymptotic distributions of test statistics. When the model includes a large number of variables or the population is not from a multivariate normal distribution, the asymptotic distributions do not approximate the distribution of the test statistics very well at small sample sizes. A variety of methods have been developed to improve the accuracy of hypothesis testing at small sample sizes. However, all these methods have their limitations, specially for nonnormal distributed data. We propose a Monte Carlo test that is able to control Type I error with more accuracy compared to existing approaches in both normal and nonnormally distributed data at small sample sizes. Extensive simulation studies show that the suggested Monte Carlo test has a more accurate observed significance level as compared to other tests with a reasonable power to reject misspecified models. 相似文献