Including Interaction Effects Research Articles

Interaction effects may actually be nonlinear effects in disguise: A review of the problem and potential solutions

It is common in addictions research for statistical analyses to include interaction effects to test moderation hypotheses. Far less commonly do researchers consider the possibility that a given predictor may exert a nonlinear effect on the outcome. This lack of attention to the possible nonlinear effects of individual predictors is problematic because it may result in identification of entirely spurious interactions with other, correlated predictors. Given the commonplace practice of testing interactions, and the rarity of testing nonlinear effects, we speculate that some of the significant interactions reported in the literature may actually be spurious, reflecting only the misspecification of nonlinear effects. We outline the mathematical reasons for this problem using the relatively simple case of a quadratic regression model. Within this context, prior research by Busemeyer and Jones (1983) clearly demonstrated that quadratic effects of individual predictors can masquerade as interaction effects between correlated predictors. Furthermore, the explosive growth of mediation, moderation, and moderated mediation analyses in behavioral research makes this issue especially relevant for researchers of addiction. In this article, we (1) call further attention to the potential problems of omitting nonlinear effects in linear regression, (2) extend these findings to the more complex moderated mediation model, and (3) provide practical recommendations for applied researchers for differentiating nonlinear from interactive effects.

Robust edge states induced by electron-phonon interaction in graphene nanoribbons

The search of new means of generating and controlling topological states of matter is at the front of many joint efforts, including bandgap engineering by doping and light-induced topological states. Most of our understading, however, is based on a single particle picture. Topological states in systems including interaction effects, such as electron-electron and electron-phonon, remain less explored. By exploiting a non-perturbative and non-adiabatic picture, here we show how the interaction between electrons and a coherent phonon mode can lead to a bandgap hosting edge states of topological origin. Further numerical simulations witness the robustness of these states against different types of disorder. Our results contribute to the search of topological states, in this case in a minimal Fock space.

Assisting hand function after spinal cord injury with a fabric-based soft robotic glove

BackgroundSpinal cord injury is a devastating condition that can dramatically impact hand motor function. Passive and active assistive devices are becoming more commonly used to enhance lost hand strength and dexterity. Soft robotics is an emerging discipline that combines the classical principles of robotics with soft materials and could provide a new class of active assistive devices. Soft robotic assistive devices enable a human-robot interaction facilitated by compliant and light-weight structures. The scope of this work was to demonstrate that a fabric-based soft robotic glove can effectively assist participants affected by spinal cord injury in manipulating objects encountered in daily living.MethodsThe Toronto Rehabilitation Institute Hand Function Test was administered to 9 participants with C4-C7 spinal cord injuries to assess the functionality of the soft robotic glove. The test included object manipulation tasks commonly encountered during activities of daily living (ADL) and lift force measurements. The test was administered to each participant twice; once without the assistive glove to provide baseline data and once while wearing the assistive glove. The object manipulation subtests were evaluated using a linear mixed model, including interaction effects of variables such as time since injury. The lift force measures were separately evaluated using the Wilcoxon signed-rank test.ResultsThe soft robotic glove improved object manipulation in ADL tasks. The difference in mean scores between baseline and assisted conditions was significant across all participants and for all manipulated objects. An improvement of 33.42 ± 15.43% relative to the maximal test score indicates that the glove sufficiently enhances hand function during ADL tasks. Moreover, lift force also increased when using the assistive soft robotic glove, further demonstrating the effectiveness of the device in assisting hand function.ConclusionsThe results gathered in this study validate our fabric-based soft robotic glove as an effective device to assist hand function in individuals who have suffered upper limb paralysis following a spinal cord injury.

The relationship of Type 1 diabetes self-management barriers to child and parent quality of life: a US cross-sectional study.

Families of children and adolescents with Type 1 diabetes experience self-management challenges that negatively impact diabetes control. This study assesses whether self-management challenges are also associated with quality of life (QOL) for children and adolescents with Type 1 diabetes and their parents. Children aged 8-12 years (n = 135), adolescents aged 13-16 years (n = 132) and their parents completed QOL assessments (diabetes-specific QOL from the PedsQL Diabetes Module or the Family Impact Module, both scaled 0-100) and a validated survey of up to six self-management barriers [PRISM; scaled 1 (low) to 5 (high)]. Regression coefficients were calculated to assess the association of self-management barriers with child and adolescent diabetes-specific QOL or parent QOL, including interaction effects to assess the stability of the associations. Mean duration of diabetes was 4.7 years for children and 6.1 years for adolescents. The majority of children and adolescents did not meet target values for glycaemic control. All barriers but one (Healthcare Team Interactions) were associated with lower diabetes-specific QOL for children and adolescents, as well as lower QOL for parents (all P < 0.05). Barrier scores that were 1 unit higher were associated with diabetes-specific QOL that was 3.7-5.1 points lower for children and 5.8-8.8 points lower for adolescents, as well as QOL that was 6.0-12.6 points lower for parents. Diabetes-specific QOL was most strongly associated with 'Denial of Disease and Its Consequences' for children and with 'Regimen Pain and Bother' for adolescents. Parent QOL was most strongly associated with 'Understanding and Organizing Care'. Associations were stable across numerous demographic and disease factors. Single-unit differences in self-management barrier scores are associated with clinically meaningful differences in QOL for children and parents. Interventions specifically tailored to address individual self-management barriers may improve both diabetes control and QOL.

Compressive behavior of FRP externally wrapped R.C. column with buckling effects of longitudinal bars

In this paper, a calculation model to simulate the compressive behavior of R.C. columns with square cross-sections externally wrapped with FRP, including buckling effects of the longitudinal bars and reduction of the confinement pressure induced by the buckled compressed bars, is presented and discussed. The model distinguishes the cases of corner and side bars, calculating the different critical lengths and the critical loads. The Teng et al. (2009) model was adopted to predict the compressive behavior of FRP-confined concrete, and the Dhakal and Maekawa (2002) model was taken into account to predict the compressive behavior of longitudinal bars. The critical length and critical stress of compressed bars including interaction effects between concrete cover, stirrups and FRP wraps were calculated, distinguishing between corner and side bars. Based on the model mentioned, analytical expressions were derived to calculate the critical strain at the onset of bar buckling and the minimum thickness of FRP to prevent instability of the compressed bars. Finally, a theoretical–experimental comparison was made to validate the model.

The Relationship of Cognitive Performance and the Theta-Alpha Power Ratio Is Age-Dependent: An EEG Study of Short Term Memory and Reasoning during Task and Resting-State in Healthy Young and Old Adults.

Objective: The Theta-Alpha ratio (TAR) is known to differ based upon age and cognitive ability, with pathological electroencephalography (EEG) patterns routinely found within neurodegenerative disorders of older adults. We hypothesized that cognitive ability would predict EEG metrics differently within healthy young and old adults, and that healthy old adults not showing age-expected EEG activity may be more likely to demonstrate cognitive deficits relative to old adults showing these expected changes.Methods: In 216 EEG blocks collected in 16 young and 20 old adults during rest (eyes open, eyes closed) and cognitive tasks (short-term memory [STM]; matrix reasoning [RM; Raven's matrices]), models assessed the contributing roles of cognitive ability, age, and task in predicting the TAR. A general linear mixed-effects regression model was used to model this relationship, including interaction effects to test whether increased cognitive ability predicted TAR differently for young and old adults at rest and during cognitive tasks.Results: The relationship between cognitive ability and the TAR across all blocks showed age-dependency, and cognitive performance at the CZ midline location predicted the TAR measure when accounting for the effect of age (p < 0.05, chi-square test of nested models). Age significantly interacted with STM performance in predicting the TAR (p < 0.05); increases in STM were associated with increased TAR in young adults, but not in old adults. RM showed similar interaction effects with aging and TAR (p < 0.10).Conclusion: EEG correlates of cognitive ability are age-dependent. Adults who did not show age-related EEG changes were more likely to exhibit cognitive deficits than those who showed age-related changes. This suggests that healthy aging should produce moderate changes in Alpha and TAR measures, and the absence of such changes signals impaired cognitive functioning.

Using a Discrete-Choice Experiment Involving Cost to Value a Classification System Measuring the Quality-of-Life Impact of Self-Management for Diabetes

ObjectivesTo describe the use of a novel approach in health valuation of a discrete-choice experiment (DCE) including a cost attribute to value a recently developed classification system for measuring the quality-of-life impact (both health and treatment experience) of self-management for diabetes. MethodsA large online survey was conducted using DCE with cost on UK respondents from the general population (n = 1497) and individuals with diabetes (n = 405). The data were modeled using a conditional logit model with robust standard errors. The marginal rate of substitution was used to generate willingness-to-pay (WTP) estimates for every state defined by the classification system. Robustness of results was assessed by including interaction effects for household income. ResultsThere were some logical inconsistencies and insignificant coefficients for the milder levels of some attributes. There were some differences in the rank ordering of different attributes for the general population and diabetic patients. The WTP to avoid the most severe state was £1118.53 per month for the general population and £2356.02 per month for the diabetic patient population. The results were largely robust. ConclusionsHealth and self-management can be valued in a single classification system using DCE with cost. The marginal rate of substitution for key attributes can be used to inform cost-benefit analysis of self-management interventions in diabetes using results from clinical studies in which this new classification system has been applied. The method shows promise, but found large WTP estimates exceeding the cost levels used in the survey.

트레이닝 프로그램 차이가 농구동호인의 신체조성, 기초체력 및 무산소성 운동능력에 미치는 영향

The purpose of this study was to determine the effects of 8-weeks training programs difference conducted by basketball club members on their body composition, basic physical fitness and anaerobic capacity. 16 participants, who were all members of a nationwide amateur basketball club association, were divided into two groups of eight: Technical training group (TTG) and plyometric training group (PTG). While technical training programs were conducted three times a week for 60 minutes by TTG, plyometric training programs were gradually implemented by PTG: Three sets of 12 reps during the first week to the fourth; four sets of 15 reps during the fifth week to eighth. The results were as follows: 1. In terms of body composition, meaningful effects including interaction effects on body weight, body fat percentage, body fat amount, BMI, fat-free body mass did not appear (p>.05). 2. In terms of basic physical fitness, PTG compared to TTG showed a meaningful improvement in muscle strength, flexibility, speed, agility and balance (p 3. In terms of anaerobic capacity, PTG compared to TTG showed a meaningful improvement in maximum power and average power (p In conclusion, this study found that the plyometric training program had positive effects on basic physical fitness, anaerobic capacity of the participating basketball players, proving the plyometric training program was appropriate to improve physical strength of amateur basketball club members.

Income disparities in healthcare use remain after controlling for healthcare need: evidence from Swedish register data on psoriasis and psoriatic arthritis

We used a southern Swedish cohort of psoriasis (PSO) and psoriatic arthritis (PsA) patients and population-based referents (N = 57,800) to investigate the influence of socioeconomic and demographic factors on the probability of healthcare use and on healthcare costs when controlling for need as measured by PSO/PsA and common additional morbidities such as diabetes, depression and myocardial infarction. People with PSO/PsA were identified by ICD-10 codes in the Skåne Healthcare Register 1998–2007. Resource use and costs for years 2008–2011 were retrieved from the Skåne Healthcare Register and the Swedish Prescribed Drug Register, and socioeconomic data were retrieved from Statistics Sweden. After controlling for PSO/PsA and common additional morbidities, income, and to some extent education, had significant effects on the probability of five types of healthcare use. Overall, income showed a bell-shaped relationship to healthcare costs, with patients in income quintiles 2 and 3 having the highest mean annualized cost irrespective of model specification. Education did not have a significant effect in most specifications. Analyses including interaction effects indicated similarly higher costs across income quintiles in the PSO and PsA subgroups, though these cost differences were lower in magnitude for patients with PSO in quintile 5 and with PsA in quintile 1. In conclusion, our results show persistent socioeconomic disparities in healthcare use among a cohort of chronically ill patients and referents, even after controlling for the presence of PSO/PsA and common additional morbidities. These disparities persist even in a country with general healthcare coverage and low out-of-pocket payments.

Proportional subclass numbers in two-factor ANOVA

ABSTRACTThe between-within split of total sum of squares in one-way analysis of variance (ANOVA) is intuitively appealing and computationally simple, whether balanced or not. In the balanced two-factor setting, the same heuristic and computations apply to analyse treatment sum of squares into main effects and interaction effects sums of squares. Accomplishing the same in unbalanced settings is more difficult, requiring development of tests of general linear hypotheses. However, textbooks treat unbalanced settings with proportional subclasss numbers (psn) as essentially equivalent to balanced settings. It is shown here that, while psn permit an ANOVA-like partition of sums of squares, test statistics for main effects of the two factors generally test the wrong hypotheses when the model includes interaction effects.

The impact of conscientiousness, mastery, and work circumstances on subsequent absenteeism in employees with and without affective disorders

BackgroundHigh numbers of employees are coping with affective disorders. At the same time, ambitiousness, achievement striving and a strong sense of personal control and responsibility are personality characteristics that are nowadays regarded as key to good work functioning, whereas social work circumstances tend to be neglected. However, it is largely unkown how personality characteristics and work circumstances affect work functioning when facing an affective disorder. Given the high burden of affective disorders on occupational health, we investigate these issues in the context of affective disorders and absenteeism from work. The principal aim of this paper is to examine whether particular personality characteristics that reflect self-governance (conscientiousness and mastery) and work circumstances (demands, control, support) influence the impact of affective disorders on long-term absenteeism (>10 working days).MethodsBaseline and 1-year follow-up data from 1249 participants in the Netherlands Study of Depression and Anxiety (NESDA) in 2004–2006 was employed. Multivariate logistic regression analyses were performed, including interaction effects between depressive, anxiety, and comorbid disorders and personality and work circumstances.ResultsIn general, mastery and conscientiousness increased nor diminished odds of subsequent long-term absenteeism, whereas higher job support significantly decreased these odds. Interaction effects showed that the impact of affective disorders on absenteeism was stronger for highly conscientious employees and for employees who experienced high job demands.ConclusionsAffective disorders may particularly severely affect work functioning of employees who are highly conscientious or face high psychological job demands. Adjusting working conditions to their individual needs may prevent excessive work absence.

The Effect of Interpersonal Justice In Family And Decision Making for Healthy Life On Students’ Health Behavior

The research is about studying the effect of interpersonal justice in the family and decision making to healthy life on students’ health behavior. There are around 5 research problems have been solved, including interaction effect of both interpersonal justice in the family and decision-making to healthy life on students’ health behavior. Therefore, an ex-post facto with 2 x 2 factorial design had been applied. Each cell consisted of 21 students’ from Senior High School in East Jakarta which selected randomly. On this study, there were three instruments have been developed, Health Behavior (HB), Interpersonal Justice in the family (IJ), and Decision Making for healthy life (DM) which measured in scaling form. Its reliability respectively was .94 (HB), .93 (IJ), and .89 (DM). Data have been analyzed by applying two-way ANOVA. Research results show that there is highly significant difference of students’ health behavior between strong and weak interpersonal justice in family. Highly significant difference of students’ health behavior also found between those students’ who is high and low decision making for healthy life. Finally, there is no significant interaction effect found between interpersonal justice in family and decision making for healthy life on students’ health behavior. Based on those findings, it could be that students’ health behavior might have been affectied by interpersonal justice independently without considering students’ decision making for healthy life. If students’ health behavior would be improved, interpersonal justice in family and decision making could be taken in to consideration separately.

Home-to-work spillover and employability among university employees

Purpose The purpose of this paper is to investigate the relationship between positive and negative home-to-work spillover, i.e., home-to-work facilitation (HWF) and home-to-work conflict (HWC) with employability. Moreover, this study also examined whether the relationship between home-to-work spillover and employability varied between academic and support staff employees. Design/methodology/approach An on-line self-report questionnaire was distributed among academic (n=139) and support staff employees (n=215) working at a Dutch university for distance-learning education. Thoroughly validated measures of home-to-work spillover and employability were used. The employability measure consisted of five dimensions: occupational expertise, anticipation and optimization, personal flexibility, corporate sense, and balance. Hypotheses were tested using hierarchical multivariate regression analyses including interaction effects. Findings HWF was positively related to anticipation and optimization only, while HWC appeared to be negatively associated with all employability dimensions. As expected, the relationships between HWF and HWC on the one hand and the specific employability dimensions on the other hand were stronger for support staff employees than for academic staff employees. Originality/value This study has extended research on employability, by focusing on the home context of employees as a possible antecedent. So far, studies have largely ignored the home context of employees, when investigating employability outcomes. Another contribution was the focus on both positive (facilitation) and negative (conflict) spillover from home-to-work, whereas previous studies mainly focused on one type of spillover only. Finally, the authors had the unique opportunity to compare support staff and academic staff employees in one and the same study.

Ethnic and Immigrant Differences in Environmental Values and Behaviors

ABSTRACTWe report results from a decade of nationwide surveys of New Zealand registered voters and an application of the Natural Area Value Scale that identify differences between a limited set of ethnic groups and between people born in New Zealand and immigrants. Ethnicity and birthplace were important determinants of environmental orientations as measured by Natural Area Value Scale factor scores, perceptions of the state of a large number of environmental domains, and engagement in pro-environmental behaviors. Our analysis highlights the importance of including interaction effects between ethnicity, immigrant status, and sociodemographic attributes. Results are consistent across environmental domains and activities, supporting the existence of fundamental interethnic differences in environmental perceptions, orientations, and behaviors.

How the choice of safety performance function affects the identification of important crash prediction variables

Across the nation, researchers and transportation engineers are developing safety performance functions (SPFs) to predict crash rates and develop crash modification factors to improve traffic safety at roadway segments and intersections. Generalized linear models (GLMs), such as Poisson or negative binomial regression, are most commonly used to develop SPFs with annual average daily traffic as the primary roadway characteristic to predict crashes. However, while more complex to interpret, data mining models such as boosted regression trees have improved upon GLMs crash prediction performance due to their ability to handle more data characteristics, accommodate non-linearities, and include interaction effects between the characteristics.An intersection data inventory of 36 safety relevant parameters for three- and four-legged non-signalized intersections along state routes in Alabama was used to study the importance of intersection characteristics on crash rate and the interaction effects between key characteristics. Four different SPFs were investigated and compared: Poisson regression, negative binomial regression, regularized generalized linear model, and boosted regression trees. The models did not agree on which intersection characteristics were most related to the crash rate. The boosted regression tree model significantly outperformed the other models and identified several intersection characteristics as having strong interaction effects.

Experimental assessment of a possible microbial priming effect in a humic boreal lake

Global change models normally do not include interaction effects between different pools of recalcitrant humic organic carbon which can alter carbon cycling via their influence on biological activities. This issue is especially important in northern regions where lakes receive high inputs of allochthonous dissolved organic carbon (DOC) from the extensive surrounding peatlands. We investigated the threshold of added labile DOC necessary to promote a priming effect (PE); i.e. stimulation of bacterial metabolism with a subsequent increase in the mineralization of recalcitrant DOC and the accompanying changes in microbial community structure and function. Our study was carried out in a small highly humic lake (Mekkojarvi, southern Finland), physically divided by a plastic curtain into two experimental basins, one where fish were present (+FISH) and one that was fishless (−FISH). In each basin, we performed a factorial mesocosm experiment in which different amounts of labile DOC were supplied as cane sugar (control +6, +9, +12 mg C L−1). Our results showed no priming effect in any carbon treatment, either in +FISH or in −FISH basins, despite a decreasing trend in total DOC concentration. Bacterial abundance and production did not increase as a response to carbon additions, while mixotrophic algae increased their abundance over time. In our experiments, the organisms that benefitted most after addition of labile DOC were mixotrophic algae, which can transform carbon into biomass by obtaining inorganic nutrients through phagotrophy. This appears most likely due to strong bacterial N limitation and dependence on resource availability and stoichiometry.

Performance and decisions: immigrant–native gaps in educational transitions in Italy

Following the seminal work of Boudon [5], sociological research has conceptualized immigrant–native gaps in educational transitions as deriving from children of immigrants' poorer academic performance (primary effects) and from different decision models existing between native and immigrant families (secondary effects). The limited evidence on immigrant–native gaps in Europe indicates that secondary effects are generally positive: children of immigrants tend to make more ambitious educational choices than natives with the same prior performance. In this paper we review the different decomposition methods employed so far in the literature to tackle similar research questions, and extend the existing methodology to allow including interaction effects and taking explanatory variables under control. We apply this method to data coming from a unique Italian administrative data set. We find that children of immigrants exhibit higher likelihood to opt for vocational training over more generalist and academic programs, even when controlling for socio-economic background. A large share of the immigrant–native differentials in the probability to attend the different school programs is explained by the different prior performance distribution. However, decision models differ between groups, and, contrary to the evidence on other countries, these differences contribute to widening the existing gaps. If children of immigrants had the same social background and prior performance of their native peers, they still would be more likely to enroll in shorter and less-demanding school programs. Interestingly, these results hold true only for boys, while we find no evidence of decision effects for girls.

Selective mobility, segregation and neighbourhood effects

Selective mobility, segregation and neighbourhood effects

Selective mobility, segregation and neighbourhood effects

Selective mobility, segregation and neighbourhood effects

Selective mobility, segregation and neighbourhood effects

Selective mobility, segregation and neighbourhood effects