Effects of nonnormality on test statistics for one-way independent groups designs

The data obtained from one-way independent groups designs is typically non-normal inform and rarely equally variable across treatment populations (i.e. population variances are heterogeneous). Consequently, the classical test statistic that is used to assess statistical significance (i.e. the analysis of variance F test) typically provides invalid results (e.g. too many Type I errors, reduced power). For this reason, there has been considerable interest in finding a test statistic that is appropriate under conditions of non-normality and variance heterogeneity. Previously recommended procedures for analysing such data include the James test, the Welch test applied either to the usual least squares estimators of central tendency and variability, or the Welch test with robust estimators (i.e. trimmed means and Winsorized variances). A new statistic proposed by Krishnamoorthy, Lu, and Mathew, intended to deal with heterogeneous variances,though not non-normality, uses a parametric bootstrap procedure. In their investigation of the parametric bootstrap test, the authors examined its operating characteristics under limited conditions and did not compare it to the Welch test based on robust estimators. Thus, we investigated how the parametric bootstrap procedure and a modified parametric bootstrap procedure based on trimmed means perform relative to previously recommended procedures when data are non-normal and heterogeneous.The results indicated that the tests based on trimmed means offer the best Type I error control and power when variances are unequal and at least some of the distribution shapes are non-normal.Social Sciences and Humanities Research Council (SSHRC

An improved model for evaluating change in randomized pretest, posttest, follow-up designs

Randomized pretest, posttest, follow-up (RPPF) designs are often used for evaluating the effectiveness of an intervention. These designs typically address two primary research questions: (1) Do the treatment and control groups differ in the amount of change from pretest to posttest? and (2) Do the treatment and control groups differ in the amount of change from posttest to follow-up? This study presents a model for answering these questions and compares it to recently proposed models for analyzing RPPF designs due to Mun, von Eye, and White (2009) using Monte Carlo simulation. The proposed model provides increased power over previous models for evaluating group differences in RPPF designs.Social Science and Humanities Research Council (SSHRC

Students' perceptions of fairness following an academic strike

Rising rates of unionization in university settings suggest that campus labour disputes are likely to become an increasingly relevant issue. The research question in the current analysis asked which factors contributed to students’ perception of fair treatment following a university labour disruption. A longitudinal survey of students’ experiences was conducted before, during, and following a 12-week strike by teaching assistants and contract faculty at a large Canadian university. Hierarchical regression analysis revealed that students’ pre-strike satisfaction with their academic program contributed to a perception of post-strike fairness. The more students’ plans had been affected by the strike, the greater the reduction in perceived fairness. Post-strike fairness increased significantly the more students were satisfied with course remediation and the more they felt they had a faculty member to turn to following the strike. Interestingly, neither students’ levels of financial concern, nor their attitudes toward the strike, predicted perceived fairness. Implications for addressing students’ concerns in the wake of an academic labour dispute are discussed

Factors Contributing to Students’ Perceptions of Fairness Following an Academic Strike

Rising rates of unionization in university settings suggest that campus labour disputes are likely to become an increasingly relevant issue. The research question in the current analysis asked which factors contributed to students’ perception of fair treatment following a university labour disruption. A longitudinal survey of students’ experiences was conducted before, during, and following a 12-week strike by teaching assistants and contract faculty at a large Canadian university. Hierarchical regression analysis revealed that students’ pre-strike satisfaction with their academic program contributed to a perception of post-strike fairness. The more students’ plans had been affected by the strike, the greater the reduction in perceived fairness. Post-strike fairness increased significantly the more students were satisfied with course remediation and the more they felt they had a faculty member to turn to following the strike. Interestingly, neither students’ levels of financial concern, nor their attitudes toward the strike, predicted perceived fairness. Implications for addressing students’ concerns in the wake of an academic labour dispute are discussed.  Les taux croissants de syndicalisation dans l’environnement universitaire conduisent à penser que les conflits de travail sur les campus vont devenir un problème de plus en plus important. Le sujet de recherche dans l’analyse en cours est de voir quels facteurs contribuent à la perception par les étudiants d’un juste traitement à la suite d’une perturbation causée par un conflit de travail. Une étude longitudinale des expériences des étudiants a été réalisée, avant, pendant et à la suite d’une grève de 12 semaines par les démonstrateurs (teaching assistants) et chargés de cours d’une grande université canadienne. Une analyse de régression hiérarchique montra que la satisfaction par les étudiants de leur programme académique avant la grève, contribuait à la perception d’équité après la grève. La perception d’équité post-grève était d’autant plus réduite que les plans de étudiants avaient été affectés par la grève. Le sentiment d’équité post-grève augmentait d’autant plus que les étudiants étaient satisfaits des moyens de pallier aux cours et qu’ils avaient un professeur à qui s’adresser après la grève. Il est intéressant de noter que ni le niveau des préoccupations financières des étudiants, ni leur attitude envers la grève ne permettrait de prédire leur perception de l’équité. Les implications concernant les préoccupations des étudiants à la suite d’un conflit de travail universitaire, furent discutées

Student stress and coping following a university strike in Canada

Questionnaires were distributed to undergraduate students to determine the relationship of a community strike to students’ academic work, social and recreational behavior, emotions, and attitudes toward the university. Results indicated that the labor dispute significantly affected students, interrupting their academic and career progress, worsening their financial situations, and increasing their recreational and social activities. Path analysis tested a model examining the relationships among students’ attitudes, emotions, and coping ability. Greater adaptiveness in coping was associated with reduced anger and anxiety, and with greater satisfaction with York University’s academic program. The more students’ plans had been affected by the labor dispute, the more anger and anxiety was felt, and the less students expressed satisfaction with the academic program at the university. Moreover, the more students felt they had been treated unfairly during the job action, the angrier they felt