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<p> In this project we used structural equation modeling to analyze the data collected for the Canadian Community Health Survey (CCHS) Cycle 1.2 - Mental Health and Well-Being conducted by Statistics Canada. The data are cross-sectional.</p> <p> We looked at the relation between depression and obesity adjusting for gender, socioeconomic status, gene-environment interactions, eating and physical activity and stress.</p> <p> We used the AMOS and Mplus softwares to analyze our data. The first one used continuous variables for depression ("persistence of depression", in years) and obesity ("body mass index"-BMI), while the second used categorical variables: lifetime depression, 12 month depression and obesity (normal weight, overweight and obese). We also used two variables to measure different aspects of stress: self-perceived ability to handle an unexpected problem and work stress-social support.</p> <p> We fitted the models across the entire data, but also across different groups: males versus females and groups based on gender and BMI.</p> <p> The results indicated that the relationship between depression and obesity is different across gender.</p> <p> The limitations of the study are also discussed. </p> / Thesis / Master of Science (MSc)

In this project we used structural equation method to analyze the data collected during the period of re-engineering in hospitals in Ontario 1995 to 1997. We want to understand how organizational change affect the well being of the staff of large teaching hospital. Two main models were considered in this project: cross-sectional models and longitudinal models for the data collected in 1995 and 1997. We tested six models for each year's data in cross-sectional model, effect-indicator, cause-indicator and mixed-indicator were used in both standard and non-standard models. We explored standard model with effect-indicators in our longitudinal case. The study was carried by SAS software program. We demonstrated an important association of job stressors with psychological outcomes of hospital staff directly and indirectly via interference. Decision-making capacity was associated with psychological outcomes in the opposite direction. Similar results were concluded from longitudinal model. The limitation was discussed. / Thesis / Master of Science (MS)

The demand for workers with college level training in computer related skills is growing rapidly. Although the number of computer science jobs is growing, the percentage of these jobs currently held by women is lower than in 1983 (Commission on Professionals in Science and Technology, 2004). The underrepresentation of women and minorities in postsecondary computing education has become a major national concern (Cohoon & Aspray, 2006). Despite a growing literature on women in STEM fields, there is a lack of theoretical development about women's participation and attrition in computer related majors. The findings are often inconsistent and there are few discipline-specific guidelines for policy. An important next step is to examine these insights with confirmatory quantitative methods. Larsen and Stubbs (2005) argue that efforts to increase diversity in computer fields should be broad-based and move beyond gender. Factors that are successful in attracting and retaining a diverse population of undergraduates in computer related majors will also benefit women and minorities. The purpose of this quantitative study was to develop and test a model of factors influencing the satisfaction and persistence of undergraduates in computer related majors at two universities in Virginia. There were three major independent constructs: academic, social, and institutional factors. Dependent constructs were persistence and satisfaction. The sample was a convenience sample of classes at differing academic levels. A total of 388 students in computer-related majors were surveyed during regularly scheduled class sessions. Data analysis was conducted using structural equation modeling (SEM) techniques. The goal of SEM is to determine the extent to which a theoretical model is supported by data. Both measurement and structural models were tested. Results indicate that these factors have significant and substantive effects on satisfaction and persistence. They highlight the importance of faculty, peers, and family support for student satisfaction and retention, and the need to examine instruction and content in computer related majors. The findings suggest the need for further work in the measurement of the constructs, and for further refinement of the final model. In addition, comparison of individual item means suggest that models may vary significantly among majors and between white and minority students. Future research should continue to test and refine the model for the influence of academic, social, and institutional factors on student satisfaction and persistence in computer related majors so that educators and policy makers can enhance the academic and social support structures for students in these majors. / Ph. D.

The goal of this research is to construct causal gene networks for genetical genomics experiments using expression Quantitative Trait Loci (eQTL) mapping and Structural Equation Modeling (SEM). Unlike Bayesian Networks, this approach is able to construct cyclic networks, while cyclic relationships are expected to be common in gene networks. Reconstruction of gene networks provides important knowledge about the molecular basis of complex human diseases and generally about living systems. In genetical genomics, a segregating population is expression profiled and DNA marker genotyped. An Encompassing Directed Network (EDN) of causal regulatory relationships among genes can be constructed with eQTL mapping and selection of candidate causal regulators. Several eQTL mapping approaches and local structural models were evaluated in their ability to construct an EDN. The edges in an EDN correspond to either direct or indirect causal relationships, and the EDN is likely to contain cycles or feedback loops. We implemented SEM with genetics algorithms to produce sub-models of the EDN containing fewer edges and being well supported by the data. The EDN construction and sparsification methods were tested on a yeast genetical genomics data set, as well as the simulated data. For the simulated networks, the SEM approach has an average detection power of around ninety percent, and an average false discovery rate of around ten percent. / Ph. D.

In this study, 236 heavy-drinking college students completed measures of self-efficacy for limiting drinking, specific coping skills for limiting drinking, outcome expectancies associated both with expected effects of drinking and expected effects of limiting drinking, and retrospective drinking behavior. Confirmatory factor analyses were conducted to examine reliability and validity, as well as serving as a pre-requisite for structural equation modeling (SEM). Results were generally consistent with predictions and supported the distinction between self-efficacy and outcome expectancies. One notable exception was that positive expectancies for limiting drinking did not load heavily on the predicted expectancy construct. Three models predicting drinking were compared utilizing SEM. The first was a model in which all constructs predicted drinking with no indirect effects. The second was based upon the ideas of Kirsch (1995) and predicted that outcome expectancies influence self-efficacy judgments. The third was based upon Bandura's (1986) theory and predicted that self-efficacy judgments would instead influence outcome expectancies. Both the models based on Kirsch and Bandura appeared to better fit the data than the model with no indirect effects. Differences in model-fit between models based on Kirsch and Bandura were not large, but slightly supported the Kirsch model. Additional analyses also supported the importance of outcome expectancies in predicting drinking behavior. Implications for theory and future directions for research are discussed. / Ph. D.

High rates of medical errors are well documented within the healthcare industry. Nurses, in particular, play a critical role in the quality and safety of healthcare services. Fatigue is a factor that has been linked to stress, safety, and performance decrements in numerous work environments. Within healthcare, however, a comprehensive definition of fatigue encompassing multiple dimensions has not been considered, but is warranted since nurses perform tasks consisting of diverse physical and mental activities. As such, "total fatigue" was examined, as were interactions between its underlying dimensions and the effects of these dimensions on performance, in the context of actual and simulated nursing work. In a survey study (Chapter 2), registered nurses reported relatively high levels of mental, physical, and total fatigue, and higher levels of fatigue were associated with perceived decreases in performance. Work environment variables, such as work schedule or shift length, were also related to differences in reported fatigue levels. An experimental study investigated causal effects of mental and physical fatigue on mental and physical performance (Chapter 3). Mental fatigue affected a measure of mental performance, and physical fatigue had a negative effect on measures of physical and mental performance. A multidimensional view of fatigue that considers direct and crossover effects between mental and physical dimensions of fatigue and performance is relevant when quantifying effects of fatigue on performance. A model of the relationships between fatigue dimensions and performance in nursing was developed using structural equation modeling techniques (Chapter 4). The model supported the existence of a total fatigue construct that is directly affected by mental and physical fatigue levels. The final model also provides quantitative path coefficients defining the strength of relationships between mental and physical dimensions of fatigue, total fatigue, and mental and physical performance. The current research provides an increased understanding of fatigue levels in registered nurses across work environments, as well as the underlying causal mechanisms between dimensions of fatigue and performance decrements. The findings and the final model can aid in designing interventions to reduce or eliminate the contributions of fatigue to the occurrence of medical errors. / Ph. D.

This study seeks to offer a meaningful statement about the relative importance of self-processes and activated social capital in the process that links high school students and educational outcomes. The conceptual model for the study draws on the large and diverse body of research that aims to understand the process and effects of the interaction of the person and his or her environment. It is hypothesized that adaptive self-processes and social capital are positively related to school engagement, educational aspirations, and actual performance in school; and, that these factors mediate the effects of family background and other potential social capital on educational outcomes. The data for this study were obtained from a sample of N=1,176 in grades 9-12 from three school divisions in Virginia. Students completed the School Relationships and Experiences Survey (SRES), an instrument designed for this study. The study uses structural equation modeling (SEM) to model the relationships between the variables of interest. Data were analyzed using LISREL 8.3 (Jöreskog & Sörbom, 1993). The covariance structure models tested include both single-indicator and multiple-indicator constructs. The analysis follows the two-step procedure suggested by Anderson and Gerbing (1988). First, a measurement model was tested using confirmatory factor analysis to develop a model with acceptable fit to the data. In step two, the theoretical model of interest was specified as an a priori model. This theoretical model was then tested and revised until a theoretically meaningful and statistically acceptable model was found. In conclusion, the results of the analyses are discussed, and possible explanations for the results are proposed. Directions for future research are outlined, including the need for cross-validation of this model on additional samples of high school students. Social capital has previously been conceptualized primarily as family resources and parent-child relationships. This study provides promising initial evidence that activated social capital (education-related support received by adolescents from the broader social network) has stronger and more meaningful effects on academic engagement and other educational outcomes than the more passive indicators of social capital used in previous research. This work was supported by a doctoral fellowship from the Social Sciences and Humanities Research Council of Canada (SSHRC) and a grant from the ASPIRES program at Virginia Tech. / Ph. D.

The current study drew on a large and diverse body of literature on social capital and aimed to understand its role in the process of transition from college to work. In particular, this research studied the cumulative effects of social capital formed in high school years and college years and examined its relationship with job outcomes. The study used the National Education Longitudinal Study (NELS) to examine whether early investment in the social capital of young adolescents produced better job outcomes in their adulthood. Families and schools were two primary sources of social capital considered in the current study. Parental involvement in a young person's life, extra-curricular activities and participation in volunteer organizations were some of the forms of social capital hypothesized to influence job outcomes after college. Structural equations modeling was used to trace the effects of the presence of social capital as early as the 8th grade in shaping student's later career status. The longitudinal data measured social capital beginning in the 8th grade and every 2 years thereafter, so that the cumulative effects of the social capital resources were investigated. Overall, the hypothesized model was found to fit the data and the findings have suggested a set of positive and direct effects of social capital on job outcomes. / Ph. D.

In this study, conceptual models of young adult citizenship participation eight years post high school using Putnam's (1993) theory of social capital are tested. This study uses a longitudinal database. Specifically, the models posit that accumulation of more social capital resources during adolescence will be associated with more positive future life expectations related to educational, occupational, and family life outcomes. Subsequently, these more positive future life expectations and social capital resources will be associated with a higher degree of citizenship participation (as measured by voting behavior, community integration and volunteerism) as young adults. Measures from the 1990, 1992 and 2000 waves of the National Education Longitudinal Study (NELS:88) dataset were used. The models were examined using structural equation modeling procedures. Findings indicate that school and community social capital had mixed results regarding their effects on the final outcome variables. Teacher interactions were not found to have a statistically significant direct effect on any of the three citizenship participation outcome variables. But this result should be viewed with caution due to possible measurement problems with the construct of teacher interactions. Peer interactions did have a statistically significant, direct, effect on community integration and volunteerism, but it did not have a direct effect on voting behavior. Participation in extracurricular school activities did have a small, direct, effect on all three outcome variables. Participation in community sports activities had a positive direct effect on community integration, a small negative effect on voting behavior, and no statistically significant effect on volunteerism. Finally, participation in other types of community activities had the largest direct effects on all three citizenship participation outcome variables. The adolescent social capital variables of teacher interactions, peer interactions, and participation in other types of community activities for tenth graders did have positive, direct effects on future life expectations for twelfth graders. Extracurricular activities participation and community sports participation were not found to have an effect on future life expectations. Future life expectations were found to have a very small, but statistically significant, positive, direct effect on all three citizenship participation variables. These findings indicate that some adolescent social capital resources can have positive direct effects on the long term, young adult, educational outcome of citizenship participation. But it varies by type of social capital resource and by the particular aspect of citizenship behavior being measured. / Ph. D.