This quantitative longitudinal study sought to highlight the difference between the proportion of men and women who planned to pursue a STEM major in the fields of mathematics, natural sciences, engineering, and computer and information sciences as freshmen, as well as to determine the proportion of men and women who changed their major choice by their senior year. In addition, the researcher sought to identify women students’ unique background characteristics and college experiences that have taken place over the course of their undergraduate college career that may have predicted their declared major choice (STEM versus non-STEM) as seniors. A review of the literature, along with Astin’s Involvement Theory, encouraged the hypothesis that college experiences influence women’s college major choice: STEM versus non-STEM. Secondary data obtained from the Cooperative Institutional Research Program at the higher Education Research Institute was used. The sample was delimitated to include only full-time undergraduate students who were graduating in 2012 or 2013. Five research questions were addressed in this study. Astin’s (1993) Input-Environment-Outcome Model was used as a conceptual framework. Descriptive (frequencies and percentages) and inferential (chi-square test and discriminant analysis) statistics were used to analyze the data. The results found a statistically significant difference between the proportion of men and women who planned to pursue a STEM major as freshmen as well as the proportion of men and women who changed their major choice from STEM to non-STEM. Discriminant analysis was used to predict group membership of STEM versus non-STEM major choice among women. It was found that many variables had an impact on predicting STEM group membership among women: satisfaction with college math and science courses, high school GPA, SAT score, high self-ratings of problem-solving skills and mathematical ability, and participating in undergraduate research. There were also variables that had a greater ability of predicting non-STEM group membership. The findings from this study will hopefully inform policy and practice. Implications for policy, practice, and future research are included. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

The purpose of this library research thesis is to review the "longitudinal study" in terms of problems and present use. A preliminary search of the literature on longitudinal method revealed problems centering around two areas: (1) definition of "longitudinal study" and (2) practical problems of method itself. The purpose of this thesis then is to explore through a search of books and journals the following questions: 1. How can “longitudinal study” be defined? 2. What problems are inherent in the study of the same individuals over time and how can these problems be solved? A third question which emerges from these two is: 3. How is “longitudinal study” being used today? This thesis differentiates traditional longitudinal study from other methods of study: the cross-sectional study, the time-lag study, the experimental study, the retrospective study, and the study from records. Each of these methods of study is reviewed according to its unique problems and best uses and compared with the longitudinal study. Finally, the traditional longitudinal study is defined as the study: (1) of individual change under natural conditions not controlled by the experimenter, (2) which proceeds over time from the present to the future by measuring the same individuals repeatedly, and (3) which retains individuality of data in analyses. Some problem areas of longitudinal study are delineated which are either unique to this method or especially difficult. The following problems related to planning the study are reviewed: definition of study objectives, selection of method of study, statistical methods, cost, post hoc analysis and replication of the study, time factor in longitudinal study, and the problem of allowing variables to operate freely. Cultural shift and attrition are especially emphasized. The dilemma is examined which is posed by sample selection with its related problems of randomization and generalizability of the study, together with the problems of repeated measurements and selection of control groups. These problems are illustrated with studies from the literature. Not only are these problems delineated cut considerable evidence is shown that we have already started to accumulate data that will permit their solution. This paper presents a number of studies which have considered these problems separately or as a side issue of a study on some other topic. Some recommendations for further research in problem areas are suggested. At the same time that this thesis notes differentiation of the longitudinal study from other studies, it also notes integration of results of longitudinal studies with results of other studies. The tenet adopted here is: scientific knowledge is cumulative and not dependent on one crucial experiment. Trends in recent longitudinal studies are found to be toward more strict observance of scientific protocols and toward limitation of time and objectives of the study. When objectives of the study are well defined and time is limited to only enough for specified change to take place, many of the problems of longitudinal study are reduced to manageable proportions. Although modern studies are of improved quality, longitudinal method is not being sufficiently used today to supply the demand for this type of data. Longitudinal study is necessary to answer some of the questions in developmental psychology. We have no alternative but to continue to develop this important research tool.

Evidence suggests that the transition to postsecondary may be an important period of risk for engagement in disordered eating (DE). DE has been demonstrated to fluctuate and change course over time, however, very little research has examined factors that underlie these changes in DE. Higher negative urgency has been associated with elevated DE frequency, and preliminary evidence suggests that negative urgency may change concurrently with DE symptoms. Moreover, symptoms of depression, anxiety, and stress (DAS), are all associated with DE engagement, implicating an important role for negative affect in DE engagement. Despite this evidence, there is a paucity of literature examining the association between negative urgency and DE frequency over time, and how acute negative emotional states may moderate this relationship. The current study aimed to address this research gap by examining the association between negative urgency and DE frequency over time, and if symptoms of DAS moderate this relationship. It was hypothesized that DE frequency and negative urgency would share a significantly coupled relationship, and that symptoms of DAS would significantly moderate this relationship. Specifically, negative urgency would be more strongly coupled with DE frequency when DAS symptoms were high, as compared to when DAS symptoms were low. Two cohorts of first year undergraduate students (N = 645) completed monthly self-reports of negative urgency, symptoms of DAS, and DE frequency over their first two semesters of post-secondary study (7 months total). Multilevel Models revealed that indeed negative urgency and DE frequency share a statistically significant coupled relationship over time (p < .001), and that depressive symptoms moderate this relationship (p < .001) such that the coupled association between negative urgency and DE frequency was strengthened by depression. The current study is the first to examine how negative urgency and DE frequency co-vary over time and how negative affect moderates this association. The results illuminate the importance of considering interactions between established risk factors and negative emotional states in the engagement and frequency of DE behaviours, and offers preliminary insight into correlates of change in DE frequency over time. / Graduate

Externalizing behaviors have been shown to exhibit within-individual changes, increasing the need to identifying factors that influence such behavior to be more or less likely to occur in any given moment. The current study aimed to contribute to the understanding of mechanisms that influence externalizing behavior using an intensive longitudinal design. Demographic variables and personality traits were measured at baseline. Momentary personality states, situational context, affect, decision-making processes, and externalizing behaviors were measured three times per day for seven days in a university sample (N = 170). Results: A new measure of momentary externalizing—Momentary-Externalizing Spectrum Inventory—was created as a practically feasible measure to administer multiple times per day and its psychometric properties were investigated. Trait disinhibition-versus-constraint predicted mean levels of externalizing behaviors. Results supported the incremental utility of personality states, such that they appear to offer additional predictive power for momentary externalizing behavior over and above personality traits. Candidate proximal mechanisms such as situational factors, momentary affect, and delay discounting were shown have the ability to predict momentary externalizing behavior in an ongoing temporally varying manner. Personality traits moderated some of these relationships between candidate proximal mechanisms and momentary externalizing behavior. Implications for the understanding of externalizing behaviors were discussed while hypotheses for future research were generated.

Romantic disengagement is a disturbingly prevalent yet understudied cause of marital distress and dissolution. Existing research on disengagement has been primarily descriptive and limited by reliance on retrospective reports from already disengaged spouses. Theoretically informed prospective research to elucidate the process through which some spouses become increasingly disengaged from their partners over time is necessary to facilitate clinical intervention efforts. Thus the purpose of this research was to propose a theoretically informed model of the process of romantic disengagement and then to perform preliminary tests of pieces of the model. The model was tested in a sample of 103 married couples assessed six times over their first seven years of marriage. Pieces of the model that were tested included (1) the implication that avoidant and disengaging behaviors toward one's partner, particularly during times of need or increased stress (such as marital conflict interactions), are indicators of a process of romantic disengagement, (2) that predispositional and contextual factors interact to predict a spouse's greater tendency to behave avoidantly during couple interactions, and (3) that spouses tendency to be more avoidant with his or her partner later in marriage will be greater to the extent that avoidance is reinforced early in marriage. First, I examined whether avoidant behavior during marital conflict contributes to a process of romantic disengagement as evidenced by declines in trust and intimacy and declines in marital satisfaction. Consistent with hypotheses, I found higher conflict avoidance was associated with declines in trust and intimacy and declines in marital satisfaction. Second, I tested two predispositional (i.e., spouses' attachment avoidance and avoidant coping style) and two contextual factors (spouses' role during support interactions, and the partner's negative affect) that were expected to interact to predict whether spouses behave avoidantly during specific couple interactions. I found mixed support for hypotheses depending on spouse and interaction type. Specifically, during conflict interactions, husbands and wives with higher attachment avoidance, and wives with more avoidant coping styles, behaved more avoidantly to the extent that their partners were higher in negative affect. During supportive transactions, husbands with more avoidant coping styles were more disengaged to the extent that their wives were higher in negative affect. Third, I tested my hypothesis that a spouse will be more avoidant with his or her partner later in marriage to the extent that avoidance is reinforced early in marriage. I found partial support for this hypothesis. Husbands' disengagement during conflict interactions interacted with improved mood post-interaction to predict husbands' disengagement across interactions at 7 years of marriage. In summary, this research presents an integrated theoretical model of romantic disengagement and provides preliminary support for aspects of the model.

The primary aim of the present study was to determine whether impairment on neuropsychological measures of decision making predicts increased alcohol use among college students. It was hypothesized that poorer performance on measures of decision making would predict linear increase on indicators of alcohol consumption across the first year of college. An additional aim was to assess whether established risk factors for college student drinking would moderate the association between decision making abilities and increased alcohol consumption, with the expectation that decision making would be more strongly associated with escalation in alcohol use for participants that are male, have a family history of alcohol abuse, report a longer history of pre-college alcohol use, hold more positive alcohol expectancies, and are more impulsive. Aims were pursued in a relatively homogeneous sample of first year college students (N = 136), using a prospective, longitudinal design in which decision making and drinking were assessed at three time-points during the first year of college. Participants additionally provided sociodemographic information and completed self-report impulsivity and alcohol expectancy questionnaires at each assessment. Results showed that drinking and associated negative consequences increased over time during the participants first year in college. However, there was generally little support for the hypotheses that poor decision making abilities are a risk factor for increased alcohol consumption, and that the association is moderated by established risk factors for drinking. Results suggest the need to consider whether drinking is indeed indicative of impaired decision making and underscore the importance of including other factors, especially perceived benefits and influence of social pressure, in models of decision making striving to predict drinking among college students.

In the dissertation, a monotone spline-based nonparametric estimation method is proposed for analyzing longitudinal data with mixture distributions. The innovative and efficient algorithm combining the concept of projected Newton-Raphson algorithm with linear mixed model estimation method is developed to obtain the nonparametric estimation of monotone B-spline functions. This algorithm provides an efficient and flexible approach for modeling longitudinal data monotonically. An iterative 'one-step-forward' algorithm based on the K-means clustering is then proposed to classify mixture distributions of longitudinal data. This algorithm is computationally efficient, especially for data with a large number of underlying distributions. To quantify the disparity of underlying distributions of longitudinal data, we also propose an index measure on the basis of the aggregated areas under the curve (AAUC), which makes no distributional assumptions and fits the theme of nonparametric analysis. An extensive simulation study is conducted to assess the empirical performance of our method under different AAUC values, covariance structures, and sample sizes. Finally, we apply the new approach in the PREDICT-HD study, a multi-site observational study of Huntington Disease (HD), to explore and assess clinical markers in motor and cognitive domains for the purpose of distinguishing participants at risk of HD from healthy subjects.

Objective: This retrospective longitudinal study attempts to determine the ontogenetic patterning of nasal septal deviation and if there is a relationship between a deviated septum and facial form growth and development. Methods: Nineteen females and twenty males were selected from the Iowa Facial Growth Study. Eighteen lateral cepalometric variables were analyzed and septal deviation was quantified using a percentage of deviation. A generalized Procrustes analysis was used to scale landmarks and generate principal components. Pearson correlation coefficients were used to analyze differences in shape. A Mann Whitney U-Test was used to analyze changes in septal deviation. Results: The first three principal components explained 56.23% of the variance. Only PC1 was significantly correlated with centroid size (r=0.82, P<0.0001). Mean percentage of septal deviation (0.620% ± 0.463%) was present at the youngest age group (3-4.9 years) and increased in each age group until adulthood, defined as over the age of 20 (0.991% ± 0.519). None of the first three principal components were found to be correlated to percentage of septal deviation. Conclusions: Nasal septal deviation has been found to increase in a longitudinal sample of subjects of northern European descent. Nasal septal deviation represents a disjunction in the growth of the nasal septum with the rest of the face. The amount and timing of nasal septal deviation that can cause nasal obstructions leading to vertical growth changes was not analyzed in this study and will require future study.

This study examined the school functioning of children with asthma compared to the school functioning of children without asthma over a 9-year time span. The present study was a secondary analysis of data from one large school district in a southeastern state. Information was gathered from multiple sources, including student records and parent and teacher surveys. Variables related to academics, behavior, and teacher perception were examined. A total of 646 participants were initially included in the study. These participants included 296 students identified as having asthma and 350 students identified as not having asthma. Participants were matched on gender, race, and socioeconomic status. Results of this study indicated significant differences for various years and subjects on a standardized achievement test. However, computed effect sizes were quite low, suggesting no practical difference between the groups. Additionally, rates of special education placement differed for the groups for one school year. All other years and variables indicated no significant differences between the groups. These findings suggest that educational experience of children with asthma may not differ significantly from that of their peers without asthma. However, future research should attempt to measure variables in different ways and possibly examine cases in a more qualitative manner.

Utilization of a large, diverse sample provided a rare opportunity to advance our understanding of gender, race, and socioeconomic differences in school-based problem behavior. Yearly assessment of discipline referrals and suspensions received within the school context from 5th- through 11th-grade, as well as assessment of school dropout, provided an opportunity to examine these issues through an extended prospective longitudinal design. Results highlight the middle school transition as a time when discipline referrals and suspensions increase markedly, while student reports of connections to others, motivation, and optimism decline sharply. Results indicate that boys, African-American students, and students from low socioeconomic status backgrounds report lower levels of connections to others, motivation, and optimism in 5th-grade. Boys, African-American students, and students from low socioeconomic status backgrounds also receive more discipline referrals and suspensions from 5th-grade onward and are more likely to experience dropout. However, regardless of demographic group membership, students who report stronger connections to others, motivation, and optimism in 5th-grade receive fewer referrals and suspensions from 5th- through 11th grade, and are much less likely to dropout of school than are students who report lower levels of connections, motivation, and optimism in 5th-grade. These results highlight the need to address students' sharp declines in functioning across the middle school transition through both ecological and person-centered prevention and school restructuring efforts. Results also highlight the utility of movement away from a static, demographic based understanding of problem behavior toward a clearer understanding of person and environment factors that may underlie both between and within demographic group differences in outcomes. Placing emphasis upon factors that are potentially amenable through school based prevention efforts considerably increases the likelihood that all of our nation's children are provided with equal opportunity to achieve their fullest potential.