What ‘works’ when retracing sample members in a qualitative longitudinal study?

Attrition represents a significant obstacle to overcome in any longitudinal research project. It is, perhaps, most keenly felt when the data collected are from a qualitative study, since, unlike quantitative longitudinal research, weighting factors cannot be applied to ‘correct’ for any biases in the achieved sample and even a small number of ‘lost’ respondents can equate to a large percentage of the original sample. It is perhaps because of qualitative longitudinal research’s (QLR) reliance on, generally speaking, smaller samples that few have been able to shed much light on which re-contacting procedures are associated with achieving higher rates of retention. In this article, using data from a fifth sweep of a larger but particularly challenging cohort of 199 former probationers, we explore the strategies which helped us maintain high levels of retention in a QLR study. The article contains many practical suggestions which others planning or undertaking similar studies may find useful.     

A more general methodology for fitting global cross-ratio models for discrete longitudinal responses

In this paper, we focus on repeated measurement problems, comprising an interesting research area in statistics. We study longitudinal data which arise when outcomes are observed repeatedly on each experimental subject at several points. We focus on a marginal approach for this type of data with lack of independence among the observations proposed by Dale [Global cross-ratio models for bivariate, discrete, ordered responses. Biometrics. 1986;42(4):909–917] for bivariate, discrete, ordered responses. We propose an alternative estimation based on divergence measures to the full likelihood method proposed in that paper. Finally, a wide simulation study and a data example that illustrates the new methodology is provided.     

潜在成长模型在体育运动领域的应用

介绍了潜在成长模型的发展、类型和内容,通过分析、归纳、整理等,比较了潜在成长模型与传统t检验、方差分析、回归分析的差别,探讨了潜在成长模型研究设计的要求,通过台湾棒球职业球员薪酬成长模型说明。利用文献调查法,分析了LGM潜在成长模型在体育运动领域中应用的概况,举例说明体育运动领域应用LGM的情况,证实了未来潜在成长模型会在体育科学领域逐渐受到重视并得到快速发展。     

Effetti delle àncore di carriera sulle transizioni lavorative: uno studio esplorativo longitudinale

Riassunto

Le nuove carriere (senza confini e mutevoli) e le numerose transizioni di ruolo che ne conseguono sollevano domande sulla stabilità nel tempo dei lavoratori e la loro identità. Il concetto di àncora di carriera di Schein sembra utile in questo contesto, ma necessita ancora di ricerca empirica. Per studiare il loro ruolo è stato spedito un questionario strutturato a 173 lavoratori in transizione in un'azienda italiana di servizi, 1 e 3 mesi dopo la transizione. Al t1 sono state misurate àncore di carriera, self-efficacy e conseguenze della transizione (innovazione di ruolo, cambiamento personale, capacità di prestazione, benessere affettivo e soddisfazione per la carriera). Le conseguenze sono state misurate anche al t2. 70 persone hanno risposto sia al t1 che al t2, 32 neoassunti e 38 lavoratori in mobilità interna. I risultati mostrano che le conseguenze della transizione per le due sotto popolazioni sono determinate da àncore di carriera diverse. Più significativo è il risultato che i lavoratori in mobilità interna con almeno un'àncora di carriera percepiscono meno cambiamento personale al t2 rispetto ai lavoratori senza àncore, come predetto dalla teoria di Schein. Le differenze nelle conseguenze della transizione per neoassunti e lavoratori in mobilità possono essere spiegate sia dalla teoria della socializzazione che da quella delle àncore di carriera.     

Using multiple imputation to estimate cumulative distribution functions in longitudinal data analysis with data missing at random

In longitudinal clinical studies, after randomization at baseline, subjects are followed for a period of time for development of symptoms. The interested inference could be the mean change from baseline to a particular visit in some lab values, the proportion of responders to some threshold category at a particular visit post baseline, or the time to some important event. However, in some applications, the interest may be in estimating the cumulative distribution function (CDF) at a fixed time point post baseline. When the data are fully observed, the CDF can be estimated by the empirical CDF. When patients discontinue prematurely during the course of the study, the empirical CDF cannot be directly used. In this paper, we use multiple imputation as a way to estimate the CDF in longitudinal studies when data are missing at random. The validity of the method is assessed on the basis of the bias and the Kolmogorov–Smirnov distance. The results suggest that multiple imputation yields less bias and less variability than the often used last observation carried forward method. Copyright © 2013 John Wiley & Sons, Ltd.     

当下中国电影公司全产业链经营模式的问题和对策

谋求全产业链布局,已成为当下国内有一定实力的电影公司的集体选择.这些电影公司的全产业链经营模式主要表现为,在传统电影产业链范围内布局,开始向大电影产业链推进,并逐步拓展电影产业链关联业务.但这种全产业链经营模式,无论对于电影公司还是电影产业来说都存在着一定的问题和风险,因此,本文提出了建设专业化电影公司、实施差异化竞争、营造健康产业发展环境等对策性建议.     

介电可调薄膜材料及压控微波器件研究

利用介电可调薄膜材料的调谐特性研制的介质压控微波器件高频特性好、功率容量大、响应速度快,还有易集成、功耗小、成本低、可靠性高的特点,相比半导体管、铁氧体以及MEMS器件有明显的优势。该文系统介绍了近年来国内外介电可调薄膜材料及压控微波器件的研究进展,并结合作者的工作评述了介电可调薄膜材料和压控微波器件的应用情况。除研究最为集中的钛酸锶钡BaxSr1-xTiO3(BST)材料,还介绍了具有较高调谐率的铋基焦绿石铌酸铋镁Bi1.5MgNb1.5O7(BMN)薄膜材料,该材料介电损耗低(约0.002),介电常数适中(约86),温度系数小,是一种极具发展前景的微波介电可调材料。     

Diagnostics for elliptical linear mixed models with first-order autoregressive errors

For longitudinal time series data, linear mixed models that contain both random effects across individuals and first-order autoregressive errors within individuals may be appropriate. Some statistical diagnostics based on the models under a proposed elliptical error structure are developed in this work. It is well known that the class of elliptical distributions offers a more flexible framework for modelling since it contains both light- and heavy-tailed distributions. Iterative procedures for the maximum-likelihood estimates of the model parameters are presented. Score tests for the presence of autocorrelation and the homogeneity of autocorrelation coefficients among individuals are constructed. The properties of test statistics are investigated through Monte Carlo simulations. The local influence method for the models is also given. The analysed results of a real data set illustrate the values of the models and diagnostic statistics.     

Peer Victimization,Self‐esteem,and Ego Resilience Types in Adolescents: A Prospective Analysis of Person‐context Interactions

This study examined bidirectional, longitudinal associations between peer victimisation and self‐esteem in adolescents, and tested for moderator effects of undercontrolling, overcontrolling, and ego‐resilient personality types in these associations. Data were used from 774 adolescents ages 11–16 years who participated in a three‐wave (i.e., 2005, 2006, and 2007) longitudinal study. Structural equation modelling analyses in Mplus demonstrated that, controlling for earlier levels of self‐esteem, self‐reported peer victimization was associated with lower self‐esteem across one‐year time intervals. Vice versa, however, low self‐esteem was not predictive of subsequent self‐reported victimization. Evidence was also found for a moderator effect of personality type on the longitudinal associations between self‐esteem and victimization. Only in the subgroup of overcontrolling adolescents was lower self‐esteem related to subsequently higher levels of peer victimization; their undercontrolling and ego‐resilient peers were unaffected.