Experimental Power for Indirect Effects in Group-randomized Studies with Group-level Mediators

Mediation analyses have provided a critical platform to assess the validity of theories of action across a wide range of disciplines. Despite widespread interest and development in these analyses, literature guiding the design of mediation studies has been largely unavailable. Like studies focused on the detection of a total or main effect, an important design consideration is the statistical power to detect indirect effects if they exist. Understanding the sensitivity to detect indirect effects is exceptionally important because it directly influences the scale of data collection and ultimately governs the types of evidence group-randomized studies can bring to bear on theories of action. However, unlike studies concerned with the detection of total effects, literature has not established power formulas for detecting multilevel indirect effects in group-randomized designs. In this study, we develop closed-form expressions to estimate the variance of and the power to detect indirect effects in group-randomized studies with a group-level mediator using two-level linear models (i.e., 2-2-1 mediation). The results suggest that when carefully planned, group-randomized designs may frequently be well positioned to detect mediation effects with typical sample sizes. The resulting power formulas are implemented in the R package PowerUpR and the PowerUp!-Mediator software (causalevaluation.org).     

Childhood antecedents of Agreeableness: A longitudinal study from preschool to late adolescence

Although the consensus view is that Agreeableness originates from childhood difficultness and regulatory deficits, few studies have investigated such assumptions longitudinally. In this study, we examined this issue by assessing enduring and mediating effects of self-regulation as well as the impact of parenting behaviors on the development of Agreeableness from preschool to late adolescence. Longitudinal data from 965 Norwegian families following children from 1.5 years to 16.5 years were used. Path analyses revealed childhood difficultness at age 4 to be related to Agreeableness at age 16.5; this effect was mediated through emotion regulation in late childhood. However, such mediation effects were primarily found when parents used punitive practices towards their children. Our findings point to personality coherence throughout development.     

Multi-body dynamic coupling mechanism for generating throwing arm velocity during baseball pitching

The purpose of this study was to identify the detailed mechanism how the maximum throwing arm endpoint velocity is determined by the muscular torques and non-muscular interactive torques from the perspective of the dynamic coupling among the trunk, thorax and throwing and non-throwing arm segments. The pitching movements of ten male collegiate baseball pitchers were measured by a three-dimensional motion capture system. Using the induced-segmental velocity analysis (IVA) developed in this study, the maximum fingertip velocity of the throwing arm (MFV) was decomposed into each contribution of the muscular torques, passive motion-dependent torques due to gyroscopic moment, Coriolis force and centrifugal force, and other interactive torque components. The results showed that MFV (31.6 ± 1.7 m/s) was mainly attributed to two different mechanisms. The first is the passive motion-dependent effect on increasing the angular velocities of three joints (thorax rotation, elbow extension and wrist flexion). The second is the muscular torque effect of the shoulder internal rotation (IR) torque on generating IR angular velocity. In particular, the centrifugal force-induced elbow extension motion, which was the greatest contributor among individual joint contributions, was caused primarily by the angular velocity-dependent forces associated with the humerus, thorax, and trunk rotations. Our study also found that a compensatory mechanism was achieved by the negative and positive contributions of the muscular torque components. The current IVA is helpful to understand how the rapid throwing arm movement is determined by the dynamic coupling mechanism.     

Working mechanisms of a web-based self-management intervention for cancer survivors: a randomised controlled trial

Objective: The aim of this study was to investigate whether problem-solving skills and perceived personal control over cancer recovery mediated the intervention effects on depression and fatigue of a web-based computer-tailored intervention for cancer survivors – the Kanker Nazorg Wijzer (Cancer Aftercare Guide).

Design: Patients were recruited through 21 Dutch hospitals (November 2013–June 2014). The mediation model was tested in a randomised controlled trial with an intervention group (n = 231) and a waiting list control group (n = 231).

Main outcome measures: Hypothesised mediators problem-solving skills (SPSI-R) and personal control (IPQ-R) were measured at baseline and 3 months from baseline. Outcomes depression (HADS) and fatigue (CIS) were measured at baseline and 6 months from baseline.

Results: The intervention effects in decreasing depression and fatigue were mediated by personal control. Problem-solving skills did not mediate the intervention effects on depression and fatigue.

Conclusion: While personal control in the control group decreased in the first three months after baseline, levels of personal control within the intervention group were maintained. This effect partially explained the intervention effects on depression and fatigue. The results provide evidence for the relevance of addressing personal control in web-based interventions in order to improve psychosocial well-being in early cancer survivors.     

初中生应对方式、压力对社会适应的影响:纵向中介模型

青春期的适应问题及其影响因素历来是研究者关注的焦点。本研究对369名初中生从初一到初三的应对方式、压力、社会适应进行了四次调查,通过纵向中介模型考察应对方式、压力对社会适应的影响。结果表明：初一时期的积极应对方式能够直接提高初三时期的积极适应水平,直接降低消极适应水平;初一时期的消极应对方式会通过提高后期的压力间接提高初三时期的消极适应水平。     

Higher-order latent trait models for cognitive diagnosis

Higher-order latent traits are proposed for specifying the joint distribution of binary attributes in models for cognitive diagnosis. This approach results in a parsimonious model for the joint distribution of a high-dimensional attribute vector that is natural in many situations when specific cognitive information is sought but a less informative item response model would be a reasonable alternative. This approach stems from viewing the attributes as the specific knowledge required for examination performance, and modeling these attributes as arising from a broadly-defined latent trait resembling theϑ of item response models. In this way a relatively simple model for the joint distribution of the attributes results, which is based on a plausible model for the relationship between general aptitude and specific knowledge. Markov chain Monte Carlo algorithms for parameter estimation are given for selected response distributions, and simulation results are presented to examine the performance of the algorithm as well as the sensitivity of classification to model misspecification. An analysis of fraction subtraction data is provided as an example. This research was funded by National Institute of Health grant R01 CA81068. We would like to thank William Stout and Sarah Hartz for many useful discussions, three anonymous reviewers for helpful comments and suggestions, and Kikumi Tatsuoka and Curtis Tatsuoka for generously sharing data.     

Self‐regulation and well‐being: The influence of identity and motives

The relationship between self‐regulatory capacities and self‐esteem as well as well‐being is examined by a mediation model that views self‐regulation as promoting the development of identity achievement which, in turn, is expected to be associated with well‐being. Among secondary school students (Study 1) identity achievement mediated the association between the self‐regulatory capacity of attention control and self‐esteem. In Study 2 (university students), the mediational effect of identity achievement was found for the relationship between the self‐regulatory capacity of action control and well‐being. Explicit motives moderated this association. In sum, a firm identity enhances well‐being by lending a sense of continuity to one's life. However, explicit motives have a substitution effect by giving direction to life when lacking firm identity commitments. Copyright © 2010 John Wiley & Sons, Ltd.     

The relationship between psychological contract breach and organizational commitment: Exchange imbalance as a moderator of the mediating role of violation

This study tested the mediating role of violation in the relationship between breach and both affective and continuance commitment and the extent to which this mediating role is moderated by exchange imbalance amongst a sample of 103 sales personnel. Results suggest that violation mediated the relationship between breach and commitment. Also, results suggest that perceived exchange imbalance moderates this mediating pathway: Low exchange imbalance increases the mediating role of violation in the case of affective commitment. On the other hand, exchange imbalance failed to moderate the mediating influence of violation in the case of continuance commitment. Results are discussed in view of the importance of a) including both measures of violation and breach in future studies and b) the role of social exchange in explaining psychological contract violation.     

Topographical and functional properties of precursors to severe problem behavior

A literature search identified 17 articles reporting data on 34 subjects who engaged in precursors to severe problem behavior, which we examined to identify topographical and functional characteristics. Unintelligible vocalization was the most common precursor to aggression (27%) and property destruction (29%), whereas self- or nondirected movement was the most common precursor to SIB (32%). Unintelligible vocalization and object-directed movement were the most common precursors to behavior maintained by social-positive reinforcement (27% each), and unintelligible vocalization was the most common precursor to behavior maintained by social-negative reinforcement (29%). Only one precursor was reported for behavior maintained by automatic reinforcement.     

有调节的中介模型检验方法：竞争还是替补?

在心理和其他社科研究领域, 经常遇到中介和调节变量。模型的变量多于3个时, 可能同时包含中介和调节变量, 一种常见的模型是有调节的中介模型。本文检视文献上各种检验有调节的中介模型的方法, 理清方法之间是竞争关系(分清优劣)还是替补关系(分清先后), 在此基础上总结出检验有调节的中介模型的步骤, 并用一个实例进行演示。文中也讨论了有调节的中介模型与有中介的调节模型的联系与区别。