Testing Variance Components in Linear Mixed Modeling Using Permutation

Abstract

Inference of variance components in linear mixed modeling (LMM) provides evidence of heterogeneity between individuals or clusters. When only nonnegative variances are allowed, there is a boundary (i.e., 0) in the variances’ parameter space, and regular inference statistical procedures for such a parameter could be problematic. The goal of this article is to introduce a practically feasible permutation method to make inferences about variance components while considering the boundary issue in LMM. The permutation tests with different settings (i.e., constrained vs. unconstrained estimation, specific vs. generalized test, different ways of calculating p values, and different ways of permutation) were examined with both normal data and non-normal data. In addition, the permutation tests were compared to likelihood ratio (LR) tests with a mixture of chi-squared distributions as the reference distribution. We found that the unconstrained permutation test with the one-sided p-value approach performed better than the other permutation tests and is a useful alternative when the LR tests are not applicable. An R function is provided to facilitate the implementation of the permutation tests, and a real data example is used to illustrate the application. We hope our results will help researchers choose appropriate tests when testing variance components in LMM.     

It’s a journey: from media effects to dynamic systems

ABSTRACT

This paper aims to demonstrate how an analytical paradigm shift from the General Linear Model (GLM) used in most communication processes and effects research to dynamic systems theory (DST, a nonlinear mathematical theory), fundamentally changes one’s research assumptions and research questions and leads to novel approaches to research design, data collection, and analysis. Concrete examples demonstrating these changes are drawn from the co-viewing literature. In addition, we discuss how data collected and interpreted using the GLM can be re-analyzed and re-interpreted to further inform our understanding of communication behavior when we use the assumptions of dynamic systems theory to derive new predictions.     

Psychosocial–Environmental Risk Factors for Suicide Attempts in Adolescents with Suicidal Ideation: Findings from a Sample of 73,238 Adolescents

We determined risk factors that discriminate between suicide attempt (SA) adolescents and suicidal ideation only (SI only) adolescents using data from the 2010 Korea Youth Risk Behavior Web‐based Survey (12–19 years; N = 73,238). In males, heavy alcohol use, drug use, and high perceived sadness/hopelessness showed significant effects on the presence of SA versus the presence of SI only. In females, along with these variables, low academic achievement, poor perceived health status, high perceived stress, and unhealthy coping strategy were also significantly related to the presence of SA versus SI only. Therefore, clinical interventions targeting adolescents' psychological distress are warranted to prevent suicide.     

周恩来党建理论与党的先进性建设

周恩来在长期的革命和建设的实践中,提出了一整套关于加强党的建设的理论,是我们党的建设的宝贵财富和巨大资源。周恩来的党建理论,对我们加强党的先进性建设,全面推进党的建设新的伟大工程具有重大的现实指导意义。     

An experimental investigation on a nanoporous carbon functionalized liquid damper

The behaviour of a p-xylene-based lyophobic nanoporous carbon system under high hydrostatic pressures is investigated. As the pressure is increased to a critical value, the nanopore surfaces between graphene layers are exposed to the liquid phase, leading to a considerable increase in solid–liquid interfacial energy. During unloading, defiltration does not occur until the pressure is much lower. Thus, the system is energy absorbing. Owing to the large solid–liquid contact area, the energy absorption efficiency is much higher than that of conventional dampers.     

Evidence for the Phase Transition from Rule I to Rule II on the Balance Scale Task

A central and recurrent theme in developmental psychology is the question whether development proceeds continuously or discontinuously. This question is difficult to answer because the two types of development may be hard to distinguish. To investigate whether change is discontinuous, one requires a formal model for discontinuous development. Such a model should provide operational, empirical criteria to investigate the nature of development. The cusp model, which is derived from catastrophe theory, is a formal model of discontinuity that provides such criteria. Eight criteria, so-called catastrophe flags, can be derived from the model. Some of these flags are predicted in other models of discontinuity, but others, notably hysteresis, are unique to catastrophe theory. In the present research, it is tested whether the transition from Rule I to Rule II on the balance scale task proceeds discontinuously. The present research centers around five catastrophe flags: bimodality, inaccessible region, sudden jump, divergence, and hysteresis. Two experiments are reported. In Experiment 1, a paper-and-pencil version of the balance scale task was administered to 314 children who were 6 to 10 years old. In Experiment 2, an adapted version of the test was administered to 302 children who were 6 to 10 years old. Bimodality, inaccessible region, hysteresis, and sudden jump were clearly observed. Divergence was not observed. The presence of four of the five flags strongly supports the hypothesis that the transition from Rule I to Rule II is discontinuous.     

小经文献与伊斯兰教相关问题研究

小经是回等民族使用的一种阿拉伯字母体系拼音文字,而用小经译、撰的文献具有丰富的内容,是研究中国伊斯兰教重要的关注点。但以往,学者研究中国伊斯兰教所依据的资料主要为汉译著述,由此来说明中国伊斯兰教的特点,却忽视了小经文献的研究,结果其所研究的成果反映的是汉译著述,并不是伊斯兰教的全部。笔者以为有必要研究小经文献所反映的伊斯兰教内容。这些内容对中国特色的伊斯兰教起到有益的补充,且为我们全面认识中国伊斯兰教提供了另一门径。