Model Selection with the Linear Mixed Model for Longitudinal Data

Model building or model selection with linear mixed models (LMMs) is complicated by the presence of both fixed effects and random effects. The fixed effects structure and random effects structure are codependent, so selection of one influences the other. Most presentations of LMM in psychology and education are based on a multilevel or hierarchical approach in which the variance-covariance matrix of the random effects is assumed to be positive definite with nonzero values for the variances. When the number of fixed effects and random effects is unknown, the predominant approach to model building is a step-up method in which one starts with a limited model (e.g., few fixed and random intercepts) and then additional fixed effects and random effects are added based on statistical tests. A model building approach that has received less attention in psychology and education is a top-down method. In the top-down method, the initial model has a single random intercept but is loaded with fixed effects (also known as an “overelaborate” model). Based on the overelaborate fixed effects model, the need for additional random effects is determined. There has been little if any examination of the ability of these methods to identify a true population model (i.e., identifying the model that generated the data). The purpose of this article is to examine the performance of the step-up and top-down model building approaches for exploratory longitudinal data analysis. Student achievement data sets from the Chicago longitudinal study serve as the populations in the simulations.     

Kinetic study of static recrystallization in an Fe–Al–O ultra-fine-grained nanocomposite

A nearly abrupt coarsening of grains is observed in a newly developed Fe–Al–O ultra-fine-grained nanocomposite with a significant volume fraction (4%) of alumina nano-precipitates. The microstructure of the alloy was analysed in different states (as-received and annealed) by means of scanning electron microscopy, transmission electron microscopy (TEM) and hardness. The initial grain size 150–200 nm increases up to 50 μm during annealing 1000 °C/8 h and thereafter demonstrates saturation. A linear correlation between volume fraction of coarse grains and hardness was found. It was identified by TEM that alumina nano-precipitates stabilize the dislocation microstructure against recovery very effectively and the grain coarsening is due to fast growth of very few dislocation free grains. Thus, the observed grain coarsening has the attributes of static recrystallization.     

Visual properties and memorising scenes: Effects of image-space sparseness and uniformity

Previous studies have demonstrated that humans have a remarkable capacity to memorise a large number of scenes. The research on memorability has shown that memory performance can be predicted by the content of an image. We explored how remembering an image is affected by the image properties within the context of the reference set, including the extent to which it is different from its neighbours (image-space sparseness) and if it belongs to the same category as its neighbours (uniformity). We used a reference set of 2,048 scenes (64 categories), evaluated pairwise scene similarity using deep features from a pretrained convolutional neural network (CNN), and calculated the image-space sparseness and uniformity for each image. We ran three memory experiments, varying the memory workload with experiment length and colour/greyscale presentation. We measured the sensitivity and criterion value changes as a function of image-space sparseness and uniformity. Across all three experiments, we found separate effects of 1) sparseness on memory sensitivity, and 2) uniformity on the recognition criterion. People better remembered (and correctly rejected) images that were more separated from others. People tended to make more false alarms and fewer miss errors in images from categorically uniform portions of the image-space. We propose that both image-space properties affect human decisions when recognising images. Additionally, we found that colour presentation did not yield better memory performance over grayscale images.     

Executive turnover: the influence of dispersion and other pay system characteristics

Using tournament theory as a guiding theoretical framework, in this study, we assess the organizational implications of pay dispersion and other pay system characteristics on the likelihood of turnover among individual executives in organizational teams. Specifically, we estimate the effect of these pay system characteristics on executive turnover decisions. We use a multi-industry, multilevel data set composed of executives in publicly held firms to assess the effects of pay dispersion at the individual level. Consistent with previous findings, we find that pay dispersion is associated with an increased likelihood of executive turnover. In addition, we find that other pay characteristics also affect turnover, both directly and through a moderating effect on pay dispersion. Turnover is more likely when executives receive lower portions of overall top management team compensation and when they have more pay at risk. These conditions also moderate the relationship between pay dispersion and individual turnover decisions, as does receiving lower compensation relative to the market.     

Multidimensional Self-Perception of Sexually Abused Girls: Factor Models and Differences Between Sexual Abuse and Comparison Groups

This study investigated the multiple dimensions of self-perception in a sample of sexually abused and nonabused comparison girls (n = 140), with particular attention to self-perception in the scholastic, social, athletic, physical (appearance), and behavioral conduct domains. First, this study examined whether the five dimensions of self-perception were psychologically discrete. Second, the relationships between the self-perception factors and childhood sexual abuse were investigated using structural equation modeling. The results supported the multidimensionality of self-perception and suggested the presence of two distinct second-order self-perception factors: academic- and social-self. While the sexually abused girls indicated less positive perception for the academic-self than the comparison group, the two groups did not differ regarding the social-self. The findings highlight the importance of a multidimensional approach to self-perception in assessing and treating sexually abused children.     

回忆日本军国主义在茅山道院犯下的罪行

今年是世界反法西斯战争胜利60周年,也是中国人民抗战胜利60周年。60多年前,日本军国主义者野蛮侵略中国,被道家誉为“第一福地,第八洞天”的茅山道院也未能逃脱魔爪。1938年农历闰七月初八的傍晚,万恶的日寇初次来到茅山道院的元符万宁宫就大肆烧杀,先用燃烧弹将华丽而高大的三清殿和西斋道院的许多楼房焚烧,又将眼睛不好的守庙居士黎洪春(解放后曾任中国道协会长黎遇航先生的父亲)带走,日寇要他带路上大茅峰,这位出家人不肯助纣为虐,拒绝从命。残暴的日军哪里由他,拖着他走,当他被推拉到华阳洞旁时,恼羞成怒的日军再也没有了耐心,将他和沿…     

Restricted Recalibration of Item Response Theory Models

Psychometrika - In item response theory (IRT), it is often necessary to perform restricted recalibration (RR) of the model: A set of (focal) parameters is estimated holding a set of (nuisance)...     

分部评分模型与其它几种多级模型的比较

项目反应理论(IRT)是当前教育与心理测量领域的一个重大进展,也日益成为当今测验领域的一个热点。本文对IRT理论中的二个重要评分模型PCM与GPCM作了简要的介绍。并较详细地对PCM与GPCM模型的逻辑结构及其适用范围进行了论述,指出了它们与其它几种重要模型之间的关系及不同之处。     

Parents Living with HIV in China: Family Functioning and Quality of Life

In China, HIV shifts the lifestyle of not only parents living with HIV/AIDS, but also their children, partners, and extended families. We examined factors related to the quality of life of parents living with HIV and the relation between family functioning and individual quality of life. Interviews were conducted with a total of 116 parents living with HIV/AIDS. Analyses of variance, Pearson correlations, and multiple regression analyses were performed to examine the relation between family functioning and quality of life. We found a significant association between family functioning and individual quality of life for parents living with HIV. In particular, family sociability had a strong relationship with the quality of life of parents living with HIV. Parents living with HIV from families where both parents are HIV-positive reported a lower level of family sociability than those from families with only one HIV-positive parent. HIV disclosure, family sociability, and number of children per family were found to be significant predictors of overall quality of life for the population. Study findings underscore the importance of developing interventions that improve family functioning for people living with HIV/AIDS in China.     

从词汇的角度看《撰集百缘经》的译者及成书年代

目前学术界对《撰集百缘经》的作者与成书年代看法不一,本文主要从文献与词汇的角度对《撰集百缘经》作一番考定。