Browsing by Subject "Longitudinal"
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Item Bayesian estimation of a longitudinal mediation model with three-level clustered data(2015-12) Israni, Anita; Beretvas, Susan Natasha; Hersh, Matthew; Pituch, Keenan; Roberts, Gregory; Whittaker, TiffanyLongitudinal modeling allows researchers to capture changes in variables that take time to exert their effects. Furthermore, incorporating mediation into a longitudinal model allows for researchers to test causal inferences about, for example, how an independent variable might affect growth in an outcome variable through growth in a mediating variable. In scenarios in which multiple variables are measured over time, the parallel process model can be used to model the inter-relationships among the measures’ trajectories where both processes are modeled to have their own separate but related growth parameters. The hierarchical linear modeling (HLM) framework can be used to model a parallel process model and allows for easy extensions to handle multiple levels and non-hierarchical data, such as cross-classified or multiple membership data structures, in clustered data. This study assessed a three-level parallel process model couched in the context of longitudinal mediation where treatment was assigned at the cluster level, matching a longitudinal cluster randomized trial design. The treatment’s effect on growth in an outcome is modeled as mediated by the growth in a mediating variable at the cluster and individual level, resulting in a cross-level and cluster-level mediated effect. A simulation and real data analysis study were conducted using a fully Bayesian analysis. In the simulation study, the following four factors were manipulated to assess the recovery of the parameters of interest: mediated effect size, random effects variance component values, number of measurement occasions, and number of clusters. Overall, relative parameter bias and statistical power improved for higher values for each of the four factors. The cross-level mediated effects were less biased and had greater statistical power than the cluster-level mediated effects. For the mediated effects that were truly zero, coverage rates based on the highest posterior density intervals showed mostly acceptable rates for the cross-level mediated effect and when path b was zero paired with a non-zero path a for the cluster-level effect. For conditions with a true value of zero for the cluster-level mediated effect with a path a of zero, the cluster-level coverage rates provided over-coverage. Results are discussed along with clarification of study limitations and suggestions for future research. Recommendations for applied researchers are also noted.Item A familial longitudinal count data study(2013-05) Goren, Hakan; Powers, Daniel A.In this report, I study familial longitudinal count data with a Poisson regression model. The data is collected from individuals who are nested in families. I focus on two main issues to fit a model. The first one is the large number of excess zeros and the second one is multi-level random effects. My approach for solving these problems are to use either Zero Inflated Poisson (ZIP) or Negative Binomial (NB) models to control for the excess zeros which allow for estimation of another parameter for over dispersion while developing the model with individual and familial random effects. First, I use a Poisson regression model with only main effects. After that, I fit a ZIP model to control for the extra zeros. I provide information about general form of the exponential families and a discussion about the dispersion parameter. I also fit a Negative Binomial model instead of the ZIP model. I also build these models with only individual random effects and with both individual and familial random effects as well. I discuss the generalized estimating equation (GEE) approach to estimate the parameters of a generalized linear model with auto regressive correlation between outcomes.Item Internalized sexualization and its consequences across the middle school years(2012-08) McKenney, Sarah Jill; Bigler, Rebecca S.; Jensen, Robert; Langlois, Judith; Swann, William; Woolley, JacquelineThe sexual content of media aimed at pre- and early adolescents (including magazines, movies, TV shows, and websites) has increased dramatically in recent years (Durham, 2008; Levin & Kilbourne, 2008; Olfman, 2009; Oppliger, 2008; Orenstein, 2011; Sarracino & Scott, 2008). Psychologists have expressed concern that exposure to such material leads to “internalized sexualization.” A recent APA Task Force (2007) called on researchers to study sexualization among pre- and early adolescent girls to understand its impact on development. For my dissertation, I sought to fulfill this mandate by completing a longitudinal study of internalized sexualization and its consequences. Ninety-nine girls and 94 boys at a private middle school were recruited for the study. They completed measures twice a year for a total of four waves of data. At each time point, girls completed measures of: (1) internalized sexualization, (2) body surveillance, (3) body shame, (4) body satisfaction, (5) general perceived self-competence, (6) physical perceived self-competence, (7) social perceived self-competence, (8) cognitive perceived self-competence, and (9) sociometric popularity. Girls’ pubertal status and grade point average (GPA) were also obtained. Boys completed the measure of sociometric popularity. Cross-sectional analyses suggested that internalized sexualization among girls increased as a function of age; however, linear growth curve modeling did not suggest intra-individual growth in internalized sexualization. Across time points, higher levels of internalized sexualization were associated with higher levels of body surveillance, body shame, and pubertal development, and lower levels of body satisfaction, general perceived self-competence, and cognitive perceived self-competence. Structural equation models suggested that increases in pubertal status temporally preceded increases in internalized sexualization, and increases in internalized sexualization temporally preceded decreases in general perceived self-competence, cognitive perceived self-competence, and GPA. Implications for intervention and social policy are discussed.Item Learning to teach, teaching to learn : a longitudinal case study of becoming a literacy teacher(2014-12) Russell, Katherine Winton; Hoffman, James V.; Maloch, BethThis longitudinal case study followed a beginning teacher from the first semester of her teacher education program into her fifth year of teaching. Using situated learning theory, this dissertation reports the influences on her journey in becoming a literacy teacher before, during, and after her teacher education program. Data sources included interviews, classroom observations, and documents that were collected over six and a half years and across multiple contexts (e.g., tutoring, student teaching, community-based learning, coursework, two elementary schools). Using constant comparative (Glaser & Strauss, 2009) and longitudinal coding methods (Saldaña, 2009), the analysis suggests that the participant developed the following understandings over time and across contexts: she intends to be a lifelong learner; she values and validates students’ interests, histories, and contributions; she is committed to teaching for social justice; and she believes a safe, trusting, and flexible community is essential to learning. Findings indicated that her ability to enact these understandings in practice, even in difficult school contexts, was made possible by her reflective stance and her commitment to surrounding herself with communities of like-minded people to support her in similar ways as had been the case in her teacher education program. The results of this study provide evidence that over time the understandings developed in a teacher education program have the potential to fully emerge in practice inside teachers’ classrooms. This study has implications for how we prepare teachers, how teacher education programs can continue to support their graduates, the types of school communities that seem to support beginning teachers, and how policy makers might direct future funding towards responsible teacher education.Item Romantic relationship dissolution and health outcomes(2016-05) McDonald, Meagan Ann; Loving, Timothy J.; Gleason, Marci; Neff, LisaThe purpose of this study was to test the prospective association between perceived social support and mental and physical health outcomes following a romantic breakup. Additionally, I tested whether an individual’s dependence on his or her partner prior to their relationships’ termination moderated the degree to which perceived social support buffered individuals from negative health outcomes following romantic relationship dissolution. I drew on an extant dataset that included 97 individuals who experienced a romantic breakup at some point during the study’s 9-month duration. All participants completed baseline measures of mental and physical health as well as perceived social support during the first six months of their romantic relationships. They also completed measures of romantic relationship dependence every two weeks up until reporting their relationship’s termination. Upon breakup, participants completed assessments of mental and physical health. Consistent with the limited research documenting a prospective link between perceived social support and mental health (and study hypothesis), social support and relationship dependence interacted to predict mental health following a breakup (controlling for baseline mental health, sex, and breakup initiator status). Results are discussed in the context of the broader social support literature and a framework for future studies on this topic is provided.