Data from longitudinal surveys give rise to many statistical challenges. They often come from a vast, heterogeneous population and from a complex sampling design. Further, they are usually collected retrospectively at intermittent interviews spaced over a long period of time, which gives rise to missing information and loss to follow-up. As a result, duration data from this kind of surveys are subject to dependent censoring, which needs to be taken into account to prevent biased analysis. Methods for point and variance estimation are developed using Inverse Probability of Censoring (IPC) weights. These methods account for the random nature of the IPC weights and can be applied in the analysis of duration data in survey and non-survey settings. The IPC estimation techniques are based on parametric estimating function theory and involve the estimation of dropout models. Survival distributions without covariates are estimated via a weighted Kaplan-Meier method and regression modeling through the Cox Proportional Hazards model and other models is based on weighted estimating functions. The observational frameworks from Statistics Canada's Survey of Labour and Income Dynamics (SLID) and the UK Millenium Cohort Study are used as motivation, and durations of jobless spells from SLID are analyzed as an illustration of the methodology. Issues regarding missing information from longitudinal surveys are also discussed.

Longitudinal data, which is also known as repeated measures, has grown increasingly within the past years because of its ability to monitor change both within and between subjects. Statisticians in many fields of study have chosen this way of collecting data because it is cost effective and it minimizes the number of subjects required to produce a meaningful outcome. This thesis will explore the world of longitudinal studies to gain a thorough understanding of why this type of collecting data has grown so rapidly. This study will also describe several methods to analyze repeated measures using data collected on the behavior of both adolescent and adult rats. The question of interest is to see if there is a change in the mean response over time and if the covariates (age, bodyweight, gender, and time) influence those changes. After much testing, our data set has a positive nonlinear change in the mean response over time within the age and gender groups. Using a model that included random effects proved to be a better method than models that did not use any random effects. Taking the log of the response variable and using day as the random effect was overall a better fit for our dataset. The transformed model also showed all covariates except for age as being significant.

The individual growth model is a relatively new statistical technique. It is now widely used to examine the trajectories of individuals and groups in repeated measures data. This study examines the association of the receptive vocabulary over time and characteristics of children who were treated for brain tumors. The children undertook different types of treatment from one to any combinations of surgery, radiation and chemotherapy. The individual growth model is used to analyze the longitudinal data and to address the issues behind the data. Results of this study present several factors' influences to the rate of change of PPVT scores. The conclusions of this thesis indicate that the decline in the PPVT scores is associated with gender, age at diagnosis, socioeconomic status, type of treatment and Neurological Predictor Scale.

To address the pervasive concerns of educators about the social and emotional effects of mathematics acceleration on students and the paucity of findings on those issues, 6 students who had participated in 6 years of accelerated mathematics courses were purposefully identified and interviewed in this longitudinal study. Through a qualitative research design, using phenomenological methods, and accompanying descriptive statistics, the author elicited the students’ descriptions of their learning experiences. Major findings in this study were that all students described great benefits from the experience, negative effects were minor, and key factors contributing to success were work ethic, motivation, parents and teachers. The researcher examines a subset of able and promising students who experienced increased mathematics expectations, and she gives parents, educators and policymakers insight into how that population responded to those challenges. In the ever-shifting arena of higher learning expectations for all students under No Child Left Behind legislation and the poor showing of U.S. students on international tests, these results provide information about the possible responses that other students, those struggling and unmotivated, might have to those demands.

Various dimensions of perfectionism are proposed, but are seldom integrated. This research develops and tests an integrative theory of perfectionism. Theory predicts personality traits (perfectionistic concerns, but not perfectionistic strivings) precede and predict changes in characteristic adaptations (perfectionistic self-presentation and perfectionism cognitions). Theory also predicts characteristic adaptations precede and predict decreases in subjective well-being (SWB), and are associated with a particular patterned form of perfectionistic narrative identity (i.e., heightened agency and lowered communion). This research tests this integrative theory. A sample of 127 emerging adults (ages 18-25) transitioning to university for the first time was recruited (78% female; 81% Caucasian). A 3-wave, 130-day longitudinal design with quantitative and qualitative components was used. Participants completed questionnaire measures of perfectionism and subjective well-being at all waves, and completed semi-structured life story interviews at Waves 1 and 3. Interviews were transcribed and coded for themes of agency (i.e., themes of achievement, status, power, and self-mastery) and communion (i.e., themes of love, dialogue, caring, and community). Results are presented in Chapters 2, 4 and 5. In Chapter 2, perfectionistic concerns led to increased perfectionistic self-presentation, which in turn led to decreases in SWB. In contrast, perfectionistic strivings did not predict longitudinal change in perfectionistic self-presentation or SWB. These findings supported hypotheses. In Chapter 4, perfectionistic concerns and perfectionism cognitions were positively correlated with agency. Perfectionism cognitions mediated the relationship between perfectionistic concerns and agency. A qualitative thematic analysis revealed themes of agency focused on performance-related concerns, with undertones of self-doubt and unrealistic high standards. These findings supported hypotheses. In Chapter 5, perfectionistic concerns and SWB were unrelated to communion, contrary to expectations. However, themes of communion exhibited good inter-rater reliability, test-retest reliability, and face validity. Hypotheses regarding communion were not supported. Overall, most hypotheses were supported. By conceptualizing perfectionistic personality as a dynamic, multifaceted, and integrated system, there are numerous implications for developmental, clinical, and personality psychology. These implications, along with the strengths and limitations of this study, are discussed.

No description available.

The objectives of this thesis is to explore different approaches of modelling clustered correlated data in the form of repeated or longitudinal counts data leading to a replicated Poisson process. The specific application is from repeated epileptic seizure time to events data. Two main classes of models will be considered in this thesis. These are the marginal and subject or cluster specific effects models. Under the marginal class of models the generalized estimating equations approach due to Liang and Zeger (1986) is first considered. These models are concerned with population averaged effects as opposed to subject-specific effects which include random subject-specific effects such that multiple or repeated outcomes within a subject or cluster are assumed to be independent conditional on the subject−specific effects. Finally we consider a distinct class of marginal models which include three common variants namely the approach due to Anderson and Gill (1982), Wei et al (1989) and Prentice et al. (1981) / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Thèse diffusée initialement dans le cadre d'un projet pilote des Presses de l'Université de Montréal/Centre d'édition numérique UdeM (1997-2008) avec l'autorisation de l'auteur.

The aim of this study was to test for prospective relationships between personality factors measured in elementary school and drinking, smoking, and binge eating during the first year of middle school. Data were collected among adolescents drawn from 23 elementary schools and 15 middles schools in central Kentucky. In a two-wave study, 1,906 children completed questionnaire measures in the spring of 5th grade and the spring of 6th grade. After controlling for sex, pubertal status, and prior engagement in addictive behaviors, it was found that urgency at wave 1 predicted drinking, smoking, and binge eating at wave 2, and low conscientiousness at wave 1 predicted drinking and smoking at wave 2. Risky behaviors during the first year of middle school predict subsequent life problems and subsequent diagnosable addictive disorders. The finding that those behaviors can be predicted by personality factors measured in elementary school indicates the value, for risk researchers and prevention specialists, of focusing efforts on children prior to the onset of adolescence.

Alcohol use in early adolescence is associated with numerous concurrent and future problems, including diagnosable alcohol use disorders. The trait of negative urgency, the tendency to act rashly when distressed, is an important predictor of alcohol-related dysfunction in youth and adults. The aim of this study was to test a model proposed by Cyders and Smith (2008) specifying a puberty-based developmental increase in negative urgency, which in turn predicts subsequent increases in early adolescent drinking. In a sample of 1,910 youth assessed semi- annually from spring of 5th grade through spring of 8th grade, we found support for this model. Pubertal onset was associated with both a mean increase and subsequent rises in negative urgency over time. Drinking frequency at any wave was predicted by prior wave assessments of drinking frequency, negative urgency, and pubertal onset. The slope of increase in drinking also increased as a function of pubertal onset. This model applied to negative urgency but not to other impulsivity-related traits. These findings highlight the importance of personality change in early adolescence as part of the risk matrix for early onset alcohol consumption.