We propose methods for analyzing longitudinal data, obtained in clinical trials and other applications with repeated measures of responses taken over time. Common characteristics of longitudinal studies are correlated responses and observations taken at unequal points in time. The first part of this dissertation examines the justification of a block bootstrap procedure for the repeated measurement designs, which takes into account the dependence structure of the data by resampling blocks of adjacent observations rather than individual data points. In the case of dependent stationary data, under regular conditions, the approximately studentized or standardized block bootstrap possesses a higher order of accuracy. With longitudinal data, the second part of this dissertation shows that the diagonal optimal weights for unbalanced designs can be made to improve the efficiency of the estimators in terms of mean squared error criterion. Simulation study is conducted for each of the longitudinal designs. We will also analyze repeated measurement data set concerning nursing home residents with multiple sclerosis, which is obtained from a large database termed the minimum data set (MDS).

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 267-293).

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xiii, 116 p.; also includes graphics. Includes abstract and vita. Advisor: H.N. Nagaraja, Dept. of Statistics. Includes bibliographical references (p. 113-116).

The 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. / text

Introduction: The process by which children's bones grow has not been fully charcterised. The current dogma is that girls fill in their medullary canal area by forming bone at the endosteum. It has been argued that the sex difference in how bone strength is conferred -- favouring boys -- may contribute to the relative protection that aging men have over aging women with respect to fracture incidence and the prevalence of osteoporosis. Primary Objectives: 1)To compare bone surface changes at the periosteal and endosteal surface of the tibial midshaft in boys and girls. 2)To compare how bone density at the tibial midshaft is accrued in boys and girls. 3) To compare sex differences in bone strength accrual. Methods: Design and Participants: Participants were obtained from a 20-month randomized, controlled school-based physical activity intervention. As we found no difference in the effect of the intervention on pQCT bone outcome variables, both groups were combined for our current study. A total of 183 participants (93 boys, 89 girls) received a pQCT scan at baseline. Results: Sex-specific comparisons of the pQCT bone outcome variables showed significantly greater rates of change (slope) for boys for the total area (ToA), cortical area (CoA), medullary canal area (MedA) and strength-strain index (SSI) measures, p<0.001. No significant differences were observed for CoD, p=0.904. The magnitude of these differences is 60.8% for ToA, 55.7% for CoA, 75.6% for MedA, 1.3% for CoD, and 54.7% for SSI. Examination of differences between the sexes (intercept) revealed significant differences with greater gains observed for boys for all measures p<0.001 except for CoD where girls exhibited greater gains p<0.001. Conclusion: Girls showed a similar pattern of cortical bone growth at the tibial midshaft- periosteal apposition dominated over endosteal resorption. Boys' increased changes and pattern of growth were of a greater magnitude at both surfaces compared to girls. This resulted in a greater increase in strength as measured by SSI in boys which can partly be explained by their larger size. Girls exhibited greater increases in CoD; however, no significant difference in the change in CoD was observed between the two.

For longitudinal data where the response and time-dependent predictors within each individual are measured at distinct time points, traditional longitudinal models such as generalized linear mixed effects models or marginal models cannot be directly applied. Instead, some preprocessing such as smoothing is required to temporally align the response and predictors. In Chapter 2, we propose a binning method, which results in equally spaced bins of time for both the response and predictor(s). Hence, after incorporating binning, traditional models can be applied. The proposed binning approach was applied on a longitudinal hemodialysis study to look for possible contemporaneous and lagged effects between occurrences of a health event (i.e., infection) and levels of a protein marker of inflammation (i.e., C-reactive protein). Both Poisson mixed effects models and zero-inflated Poisson (ZIP) mixed effects models were applied to the subsequent binned data, and some important biological findings about contemporaneous and lagged associations were uncovered. In addition, a simulation study was conducted to investigate various properties of the binning approach. In Chapter 3, asymptotic properties have been derived for the fixed effects association parameter estimates following binning, under different data scenarios. In addition, we propose some leave-one-subject-out cross-validation algorithms for bin size selection. In Chapter 4, in order to identify levels of a predictor that might be indicative of recently occurred event(s), we propose a generalized mixed effects regression tree (GMRTree) based method which estimates the tree by standard tree method such as CART and estimates the random effects by a generalized linear mixed effects model. One of the main steps in this method was to use a linearization technique to change the longitudinal count response into a continuous surrogate response. Simulations have shown that the GMRTree method can effectively detect the underlying tree structure in an applicable longitudinal dataset, and has better predictive performance than either a standard tree approach without random effects or a generalized linear mixed effects model, assuming the underlying model indeed has a tree structure. We have also applied this method to two longitudinal datasets, one from the aforementioned hemodialysis study and the other from an epilepsy study.

Graduate

In 1998, 12 students, aged 11-12 years, were identified by primary schools in a socially disadvantaged area of New Zealand as being at risk of negative life outcomes, as a consequence of known adversities in their lives. The students were interviewed, as were their parents and teachers, and they also completed learning assessments and measures of personal and social concerns. The purpose of these evaluations was to identify risk and protective factors in the young people’s lives, and to make estimations of personal resilience. In 2008, nine of the original study participants, who were now aged 21-22 years and in emerging adulthood, were located and were interviewed again. The assessments addressed the participant’s current circumstances, and what had happened for them over the last ten years. The interviews also asked the participants to reflect about 12 resilience dimensions that have been identified in the literature (Masten & Coatsworth, 1998) and whether they considered that they were personally resilient. The recent interview data were analysed using interpretative phenomenological analysis (Smith & Osborn, 2008). The individual analyses show a rich diversity of life paths and, as well, three sets of themes were identified across the case studies; and they are personal relationships, contexts of development (schooling and education, culture, religion, and jobs and careers), and personhood and identity. A resilience model was derived from the integration of the data from the first and second assessments with contemporary resilience studies and theorising. The central idea of the model is that resilient functioning is determined by the nature and quality of relationships within, and across, developmental settings. As a corollary, it is hypothesised that interpersonal relationships influence individual executive functioning, and emotional regulation in particular; and that these cognitive and affective capacities can translate into goal seeking and other constructive actions. The explanation of the resilience model leads onto recommendations for further research on relationships that enhance personal functioning. There are also suggestions for social policy that follow from the exposition, and some guidelines for professional practice with children and families.

In 1998, 12 students, aged 11-12 years, were identified by primary schools in a socially disadvantaged area of New Zealand as being at risk of negative life outcomes, as a consequence of known adversities in their lives. The students were interviewed, as were their parents and teachers, and they also completed learning assessments and measures of personal and social concerns. The purpose of these evaluations was to identify risk and protective factors in the young people’s lives, and to make estimations of personal resilience. In 2008, nine of the original study participants, who were now aged 21-22 years and in emerging adulthood, were located and were interviewed again. The assessments addressed the participant’s current circumstances, and what had happened for them over the last ten years. The interviews also asked the participants to reflect about 12 resilience dimensions that have been identified in the literature (Masten & Coatsworth, 1998) and whether they considered that they were personally resilient. The recent interview data were analysed using interpretative phenomenological analysis (Smith & Osborn, 2008). The individual analyses show a rich diversity of life paths and, as well, three sets of themes were identified across the case studies; and they are personal relationships, contexts of development (schooling and education, culture, religion, and jobs and careers), and personhood and identity. A resilience model was derived from the integration of the data from the first and second assessments with contemporary resilience studies and theorising. The central idea of the model is that resilient functioning is determined by the nature and quality of relationships within, and across, developmental settings. As a corollary, it is hypothesised that interpersonal relationships influence individual executive functioning, and emotional regulation in particular; and that these cognitive and affective capacities can translate into goal seeking and other constructive actions. The explanation of the resilience model leads onto recommendations for further research on relationships that enhance personal functioning. There are also suggestions for social policy that follow from the exposition, and some guidelines for professional practice with children and families.

Thesis (M.A.)--University of Notre Dame, 2004. / Thesis directed by Scott E. Maxwell for the Department of Psychology. "July 2004." Includes bibliographical references (leaves 132-136).