Assessing Bias in Regression Estimates Using Monte Carlo Simulations: Examples in Criminal Justice Research

Can we trust published results? Problems with bias in reported results: “Do social scientists even know anything?” Failed replications (“repligate”). Inaccurate inferences about important relationships (Type I and Type II errors). Inaccurate power analyses for future studies. To avoid these problems, researchers need tools to rigorously evaluate statistical models. The Monte Carlo method is one tool that can be used to evaluate bias in model estimateshttps://digitalscholarship.unlv.edu/gcua_symposium/1008/thumbnail.jp

An Overview of Variational Integrators

The purpose of this paper is to survey some recent advances in variational integrators for both finite dimensional mechanical systems as well as continuum mechanics. These advances include the general development of discrete mechanics, applications to dissipative systems, collisions, spacetime integration algorithms, AVI’s (Asynchronous Variational Integrators), as well as reduction for discrete mechanical systems. To keep the article within the set limits, we will only treat each topic briefly and will not attempt to develop any particular topic in any depth. We hope, nonetheless, that this paper serves as a useful guide to the literature as well as to future directions and open problems in the subject

The combined effect of feed frequency and ration size of diets with and without microbial biomass on the growth and feed conversion of juvenile Penaeus monodon

Feed management strategies that maximize shrimp growth and optimize feed utilization are critical to the cost-effectiveness of production. In this study, juvenile Penaeus monodon (~3 g) were cultured for 6 weeks in a laboratory-based clear-water tank system. The experiment design was a three-way factorial with two diets (Diet A - standard industry formulation or Diet B - the same diet with 10% microbial biomass), two feed frequencies (twice or six times daily) and three rations (60%, 80% and 100% of satiation). The results demonstrated clear growth benefits of feeding more than two times per day and feed efficiency benefits of a restricted ration. There was also a significant interaction between frequency and ration, which demonstrated that growth improved using six feeds compared with two feeds as ration amount decreased. The effects of frequency and ration were consistent for both diets; however, the addition of a microbial biomass provided significant growth improvements across all treatments. These outcomes define the gains produced by the combined effect of frequency and ration and suggest a compromise between feed utilization and feeding effort for adoption in feed management strategies

Bystanders’ Willingness to Report Crimes and Cooperate with Legal Authorities: The Role of Individual and Contextual Differences

Studies and victimization surveys suggest that many, if not most, crimes are not reported to legal authorities. The overarching aim of this project was to examine the roles of individual and contextual differences in bystanders’ willingness to report crimes to, and cooperate with, legal authorities. A sample of 1,434 adults in the U.S. completed a survey in which they read and responded to crime vignettes and responded to items theoretically measuring individual differences in legal socialization, perceived legitimacy, the need for cognitive closure, right-wing authoritarianism, social dominance orientation, and the general willingness to cooperate. Bystanders’ relationship to the victim, relationship to the suspected perpetrator, and the crime severity were experimentally manipulated between vignettes. I used latent variable models to examine the measurement structure of key concepts and the relationships between individual differences and the general willingness to cooperate; I used multilevel models to examine how both individual and situational differences predict the willingness to cooperate in hypothetical crime scenarios. Results supported multidimensional measurement models of legal socialization and perceived legitimacy, showed associations between dimensions of legal socialization and perceived legitimacy, and robust associations between dimensions of legal socialization, perceived legitimacy, and the willingness to cooperate. In addition, the need for cognitive closure, right-wing authoritarianism, and social dominance orientation explained a substantive amount of variance in the willingness to cooperate, but the relationships were different depending on the particular facet of right-wing authoritarianism and social dominance orientation and, in some instance, the relationships changed depending on situational factors, especially the relationship to the victim. The need for cognitive closure, right-wing authoritarianism, and social dominance orientation were associated with dimensions of both legal socialization and perceived legitimacy, offering empirical support for theoretical integration. Further, crime severity and the bystander’s relationship to the perpetrator had the strongest main effects on the willingness to report across different types of crime and controlling for every individual difference measure. The relationship to the victim also affected the willingness to cooperate, but the magnitude and direction of the relationship depended on individual differences. The findings both support and extend prior theory and studies. I discuss their implications, as well as limitations of the current study and directions for future research

Reliability of a 2-Bout exercise test on a Wattbike cycle ergometer

Purpose: To determine the intraday and interday reliability of a 2 × 4-min performance test on a cycle ergometer (Wattbike) separated by 30 min of passive recovery (2 × 4MMP). Methods: Twelve highly trained cyclists (mean ± SD; age = 20 ± 2 y, predicted VO2max = 59.0 ± 3.6 mL · kg–1 · min–1) completed six 2 × 4MMP cycling tests on a Wattbike ergometer separated by 7 d. Mean power was measured to determine intraday (test 1 [T1] to test 2 [T2]) and interday reliability (weeks 1–6) over the repeated trials. Results: The mean intraday reliabilities of the 2 × 4MMP test, as expressed by the typical error of measurement (TEM, W) and coefficient of variation (CV, %) over the 6 wk, were 10.0 W (95% confidence limits [CL] 8.2–11.8), and 2.6% (95%CL 2.1–3.1), respectively. The mean interday reliability TEM and CV for T1 over the 6 wk were 10.4 W (95%CL 8.7–13.3) and 2.7% (95%CL 2.3–3.5), respectively, and 11.7 W (95%CL 9.8–15.1) and 3.0% (95%CL 2.5–3.9) for T2. Conclusion: The testing protocol performed on a Wattbike cycle ergometer in the current study is reproducible in highly trained cyclists. The high intraday and interday reliability make it a reliable method for monitoring cycling performance and for investigating factors that affect performance in cycling events

Improved timber harvest techniques maintain biodiversity in tropical forests

Tropical forests are selectively logged at 20 times the rate at which they are cleared, and at least a fifth have already been disturbed in this way. In a recent pan-tropical assessment, Burivalova et al. demonstrate the importance of logging intensity as a driver of biodiversity decline in timber estates. Their analyses reveal that species richness of some taxa could decline by 50% at harvest intensities of 38 m3 ha-1. However, they did not consider the extraction techniques that lead to these intensities. Here, we conduct a complementary meta-analysis of assemblage responses to differing logging practices: conventional logging and reduced-impact logging. We show that biodiversity impacts are markedly less severe in forests that utilise reduced-impact logging, compared to those using conventional methods. While supporting the initial findings of Burivalova et al., we go on to demonstrate that best practice forestry techniques curtail the effects of timber extraction regardless of intensity. Therefore, harvest intensities are not always indicative of actual disturbance levels resulting from logging. Accordingly, forest managers and conservationists should advocate practices that offer reduced collateral damage through best practice extraction methods, such as those used in reduced-impact logging. Large-scale implementation of this approach would lead to improved conservation values in the 4 million km2 of tropical forests that are earmarked for timber extraction

Primary Prevention and Motivational Interviewing: Patterns in Athletic Training

Background: The BOC practice analysis defines the first domain as Risk Reduction, Wellness and Health Literacy including, “Promoting healthy lifestyle behaviors with effective education and communication.” There is limited evidence on primary prevention measures athletic trainers (ATs) use to address health-related behaviors. Motivational interviewing is an evidence-based patient-centered style of communication used to help patients modify detrimental health behaviors to improve health outcomes. The purpose of this study was to explore knowledge and practice patterns of primary prevention and motivational interviewing in athletic training. Methods: We used a cross-sectional, web-based survey (Qualtrics, Provo, UT). The survey contained demographic questions, a primary prevention practice patterns questionnaire, a motivational interviewing perception and practice patterns questionnaire, and the Motivational Interviewing Knowledge and Attitudes Test (MIKAT). The demographic questions, primary prevention questions, and motivational interviewing questions underwent a CVI process using five expert reviewers (CVI 0.95). The survey was distributed to 3,250 athletic trainers through the NATA Research Survey Service, where 146 individuals accessed the survey (4.5%), and social media, with 18 participants completing the survey via that route. A total of 51 participants (women=25, men=24, no response=2; age = 36±11years, years of experience = 13±11 years [range = 0-35 years]) completed the survey and were included in the final analysis. Inferential and descriptive statistics were used to analyze demographic variables, practice patterns- and education-related items. Results: Most participants used at least one primary prevention strategy (n=41, 80.4%). The most used primary prevention strategies were nutritional education (n=41, 80.4%), exercise prevention (n=41, 80.4%), and substance abuse education (n=15, 29.4%) (Table 3). Approximately half of respondents (n=27, 52.9%) received formal education/training on primary prevention strategies. Most (n=33, 64.7%) reported doing so on an individual level, while others (n=10, 19.6%) reported using it on the population/community level. Motivational interviewing was largely (n=43, 84.3%) not used as a primary prevention strategy. Conclusion: Generally, primary prevention strategies were used on an individual level, with most not using them to address health-related behaviors. To best promote healthy lifestyle behaviors, athletic trainers may need to increase the diversity of primary prevention strategies utilized, including the use of motivational interviewing techniques

Training Load, Injury Burden, and Team Success in Professional Rugby Union:Risk Versus Reward

CONTEXT: Individual and team injury burden and performance are 2 key considerations facing practitioners in the daily prescription of an athlete's training load. Whereas a considerable number of researchers have examined univariate relationships between training load and performance, training load and injury, or injury and performance, few investigators have examined all 3 concurrently. OBJECTIVE: To assess the association among training load, injury burden, and performance in professional rugby union. DESIGN: Descriptive epidemiology study. SETTING: The English Premiership competition. PATIENTS OR OTHER PARTICIPANTS: Individual injury and training load data, as well as team performance data, were captured during the 2015–2016 (n = 433 players) and 2016–2017 (n = 569 players) seasons. MAIN OUTCOME MEASURE(S): Data were aggregated into team average scores for each week, including weekly (acute) load, smoothed chronic load, changes in load, injury burden, and weekly performance. Linear mixed modelling techniques were used to assess the association among measures. RESULTS: Injury burden was negatively associated with performance, with a high weekly burden associated with a likely harmful (P = .01) decrease in performance. Training load measures displayed only trivial associations with performance. Only the acute:chronic workload ratio measure was clearly associated with injury burden, with a possibly harmful effect (P = .02). Both squad size and player availability were associated with only trivial changes in performance. CONCLUSIONS: Whereas no association between average training load and performance existed, associations between training load and injury burden and between injury burden and performance were clear. Further investigation using more sensitive and individualized measures of load, performance, and injury may elicit a clearer relationship and should be considered for future work