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1.
This Monte Carlo simulation study compares methods to estimate the effects of programs with multiple versions when assignment of individuals to program version is not random. These methods use generalized propensity scores, which are predicted probabilities of receiving a particular level of the treatment conditional on covariates, to remove selection bias. The results indicate that inverse probability of treatment weighting (IPTW) removes the most bias, followed by optimal full matching (OFM), and marginal mean weighting through stratification (MMWTS). The study also compared standard error estimation with Taylor series linearization, bootstrapping and the jackknife across propensity score methods. With IPTW, these standard error estimation methods performed adequately, but standard errors estimates were biased in most conditions with OFM and MMWTS.  相似文献   

2.
The integration of modern methods for causal inference with latent class analysis (LCA) allows social, behavioral, and health researchers to address important questions about the determinants of latent class membership. In this article, 2 propensity score techniques, matching and inverse propensity weighting, are demonstrated for conducting causal inference in LCA. The different causal questions that can be addressed with these techniques are carefully delineated. An empirical analysis based on data from the National Longitudinal Survey of Youth 1979 is presented, where college enrollment is examined as the exposure (i.e., treatment) variable and its causal effect on adult substance use latent class membership is estimated. A step-by-step procedure for conducting causal inference in LCA, including multiple imputation of missing data on the confounders, exposure variable, and multivariate outcome, is included. Sample syntax for carrying out the analysis using SAS and R is given in an appendix.  相似文献   

3.
This study investigates the relationship between early maternal employment history and children's vocabulary and inductive reasoning ability at age 5, drawing on longitudinal information on 2,200 children from the Growing Up in Scotland data. Prior research rarely addresses dynamics in maternal employment and the methodological ramifications of time‐variant confounding. The present study proposes various measures to capture duration, timing, and stability of early maternal employment and uses inverse probability of treatment weighting to control for time‐variant confounders that may partially mediate the effect of maternal employment on cognitive scores. The findings suggest only modest differences in the above ability measures between children who have been exposed to very different patterns of eary maternal employment, but with similar observed covariate history.  相似文献   

4.
考虑变系数多维线性结构关系EV模型y=xTβ(t),Y=y+ε,X=x+u,利用文[4]构造的参数β(t)在t=t0处的参数β(t0)的估计量βn(t0)构造参数σ2的估计量σn2,并证明它具有渐近正态性.  相似文献   

5.
Two hypothesized models that represent relationships among test anxiety, perceived test difficulty, and test performance observed immediately before and after a final examination were tested. The structural equation modeling was used to examine the hypothesized relationships by imposing the structure of direct and indirect effects on the current data collected from 208 undergraduate students. Students' perception of test difficulty had a significant effect on the arousal of both worry and emotionality. Temporal changes were observed in the degrees of these relationships; while test difficulty perceived before and during the exam both had effects on test anxiety perceived at each corresponding time, students' perception of test difficulty during the exam had a greater direct effect on the arousal of test anxiety than did test difficulty perceived before the exam. Worry, but not emotionality, had a strong inverse relationship with performance. That perceived test difficulty did not have a direct effect on test performance, but had an indirect effect mediated by worry, indicates that test performance was not directly influenced by how they perceive the test difficulty, but worry aroused by the difficulty perception influenced their performance. Importance of understanding students' perceived test difficulty was discussed for its effect on arousing worry anxiety.  相似文献   

6.
Structural equation modeling is a common multivariate technique for the assessment of the interrelationships among latent variables. Structural equation models have been extensively applied to behavioral, medical, and social sciences. Basic structural equation models consist of a measurement equation for characterizing latent variables through multiple observed variables and a mean regression-type structural equation for investigating how explanatory latent variables influence outcomes of interest. However, the conventional structural equation does not provide a comprehensive analysis of the relationship between latent variables. In this article, we introduce the quantile regression method into structural equation models to assess the conditional quantile of the outcome latent variable given the explanatory latent variables and covariates. The estimation is conducted in a Bayesian framework with Markov Chain Monte Carlo algorithm. The posterior inference is performed with the help of asymmetric Laplace distribution. A simulation shows that the proposed method performs satisfactorily. An application to a study of chronic kidney disease is presented.  相似文献   

7.
考虑一元线性结构关系EV模型y=a+bx,Y=y+E,X=x+u,在测量误差u和ξ的方差不相等时,对未知参数a和b进行了估计,利用重复观测数据,构造出参a,b和误差的方差的估计量,并证明了它们具有相合性.  相似文献   

8.
考虑响应变量随机缺失下线性模型响应变量均值的估计问题,分别获得了基于完全观测样本数据、线性回归插补后的"完全样本"和逆概率加权插补后的"完全样本"得到的响应变量均值估计,并证明了其渐近正态性.  相似文献   

9.
The relationships among adjustment problems, self‐efficacy, and psychological distress were investigated in a sample of 207 Chinese gifted students in Hong Kong. A mediation‐effect model specifying that adjustment problems had an effect on psychological distress mediated by self‐efficacy was hypothesized and tested using structural equation modeling procedures. For comparison, a direct‐effect model and a direct‐and‐mediation‐effect model were also fitted to the data. The results indicated that the direct‐and‐mediation‐effect model provided the best and a reasonably adequate fit, suggesting that the effects of adjustment problems on psychological distress could be direct, but more importantly the effects could also be mediated by self‐efficacy. Implications of the findings for enhancing the self‐efficacy of students to promote their psychological well‐being are discussed.  相似文献   

10.
ABSTRACT

Testlets, or groups of related items, are commonly included in educational assessments due to their many logistical and conceptual advantages. Despite their advantages, testlets introduce complications into the theory and practice of educational measurement. Responses to items within a testlet tend to be correlated even after controlling for latent ability, which violates the assumption of conditional independence made by traditional item response theory models. The present study used Monte Carlo simulation methods to evaluate the effects of testlet dependency on item and person parameter recovery and classification accuracy. Three calibration models were examined, including the traditional 2PL model with marginal maximum likelihood estimation, a testlet model with Bayesian estimation, and a bi-factor model with limited-information weighted least squares mean and variance adjusted estimation. Across testlet conditions, parameter types, and outcome criteria, the Bayesian testlet model outperformed, or performed equivalently to, the other approaches.  相似文献   

11.
In many intervention and evaluation studies, outcome variables are assessed using a multimethod approach comparing multiple groups over time. In this article, we show how evaluation data obtained from a complex multitrait–multimethod–multioccasion–multigroup design can be analyzed with structural equation models. In particular, we show how the structural equation modeling approach can be used to (a) handle ordinal items as indicators, (b) test measurement invariance, and (c) test the means of the latent variables to examine treatment effects. We present an application to data from an evaluation study of an early childhood prevention program. A total of 659 children in intervention and control groups were rated by their parents and teachers on prosocial behavior and relational aggression before and after the program implementation. No mean change in relational aggression was found in either group, whereas an increase in prosocial behavior was found in both groups. Advantages and limitations of the proposed approach are highlighted.  相似文献   

12.
将汽车保险中的一类相依两险种风险模型扩展到相依三险种风险模型，用对齐次poisson过程的稀疏与分解将该模型转化为古典风险模型，并证明了转化的合理性，进而给出破产概率的一般表达式及其一个上界估计．这种转化的方法对类似的多险种相依情形同样适用．  相似文献   

13.
The assessment of mediation in dyadic data is an important issue if researchers are to test process models. Using an extended version of the actor–partner interdependence model the estimation and testing of mediation is complex, especially when dyad members are distinguishable (e.g., heterosexual couples). We show how the complexity of the model can be reduced by assuming specific dyadic patterns. Using structural equation modeling, we demonstrate how specific mediating effects and contrasts among effects can be tested by phantom models that permit point and bootstrap interval estimates. We illustrate the assessment of mediation and the strategies to simplify the model using data from heterosexual couples.  相似文献   

14.
考虑变系数多维线性结构关系EV模型y=xτβ(t),Y=y+ε,X=x+u中的参数β(t)=(β1(t),β2(t),….,βP(t))τ的估计,利用线性模型中的M方法和权函数方法,构造出t=t0处的参数β(t0)的加权M估计量βn(t0),并证明了它具有相合性.  相似文献   

15.
Mediation is usually assessed by a regression-based or structural equation modeling (SEM) approach that we will refer to as the classical approach. This approach relies on the assumption that there are no confounders that influence both the mediator, M, and the outcome, Y. This assumption holds if individuals are randomly assigned to levels of M but generally random assignment is not possible. We propose the use of propensity scores to help remove the selection bias that may result when individuals are not randomly assigned to levels of M. The propensity score is the probability that an individual receives a particular level of M. Results from a simulation study are presented to demonstrate this approach, referred to as Classical + Propensity Model (C+PM), confirming that the population parameters are recovered and that selection bias is successfully dealt with. Comparisons are made to the classical approach that does not include propensity scores. Propensity scores were estimated by a logistic regression model. If all confounders are included in the propensity model, then the C+PM is unbiased. If some, but not all, of the confounders are included in the propensity model, then the C+PM estimates are biased although not as severely as the classical approach (i.e. no propensity model is included).  相似文献   

16.
A problem central to structural equation modeling is measurement model specification error and its propagation into the structural part of nonrecursive latent variable models. Full-information estimation techniques such as maximum likelihood are consistent when the model is correctly specified and the sample size large enough; however, any misspecification within the model can affect parameter estimates in other parts of the model. The goals of this study included comparing the bias, efficiency, and accuracy of hypothesis tests in nonrecursive latent variable models with indirect and direct feedback loops. We compare the performance of maximum likelihood, two-stage least-squares and Bayesian estimators in nonrecursive latent variable models with indirect and direct feedback loops under various degrees of misspecification in small to moderate sample size conditions.  相似文献   

17.
The present study was concerned with the development and testing of a structural equation model wherein the relation of interparental conflict to the adjustment problems of young adolescents is mediated through its impact on 3 aspects of parenting behavior: lax control, psychological control, and parental rejection/withdrawal. The model was tested separately on a sample of 46 young adolescents from intact families and a group of 51 adolescents from recently divorced families. The hypothesis that most of the relation between martial conflict and adolescent adjustment problems could be explained through perturbations in the parent-child relationship received considerable support; the only direct effect of conflict was on externalizing problems in the intact sample. The results also suggested that the mediational patterns were somewhat different for the 2 samples, and that the model accounts for a greater proportion of the variance in the adjustment problems of adolescents from intact homes than of those from recently divorced families.  相似文献   

18.
考虑变系数多维线性结构关系EV模型y=xTβ〔t〕,Y=y+ε,X=x+u,利用一般的函数ρ〔·〕.构造了参数β〔t〕=β1〔t〕,β2〔t〕,…,βp〔t〕T〕在t=t0处的参数β〔t0〕的估计量β^n〔t0〕,并证明它具有渐近正态性.  相似文献   

19.
Statistical mediation analysis is used to investigate intermediate variables in the relation between independent and dependent variables. Causal interpretation of mediation analyses is challenging because randomization of subjects to levels of the independent variable does not rule out the possibility of unmeasured confounders of the mediator to outcome relation. Furthermore, commonly used frequentist methods for mediation analysis compute the probability of the data given the null hypothesis, which is not the probability of a hypothesis given the data as in Bayesian analysis. Under certain assumptions, applying the potential outcomes framework to mediation analysis allows for the computation of causal effects, and statistical mediation in the Bayesian framework gives indirect effects probabilistic interpretations. This tutorial combines causal inference and Bayesian methods for mediation analysis so the indirect and direct effects have both causal and probabilistic interpretations. Steps in Bayesian causal mediation analysis are shown in the application to an empirical example.  相似文献   

20.
The purpose of this study is to provide guidance on a process for including latent class predictors in regression mixture models. We first examine the performance of current practice for using the 1-step and 3-step approaches where the direct covariate effect on the outcome is omitted. None of the approaches show adequate estimates of model parameters. Given that Step 1 of the 3-step approach shows adequate results in class enumeration, we suggest using an alternative approach: (a) decide the number of latent classes without predictors of latent classes, and (b) bring the latent class predictors into the model with the inclusion of hypothesized direct covariate effects. Our simulations show that this approach leads to good estimates for all model parameters. The proposed approach is demonstrated by using empirical data to examine the differential effects of family resources on students’ academic achievement outcome. Implications of the study are discussed.  相似文献   

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