The purpose of this study was to explore the relationship of dual enrollment course participation by comparing first-time, full-time traditional community college students who participated in dual enrollment (N=246) to peers (N=986) that did not participate. Dual enrollment participation was defined as taking one or more dual enrollment courses. The population for this study (N=1,232) included first-time, full-time students who graduated from public high schools in the service area of Northeast State Community College over a five year span from 2008 through 2012. Propensity score matching eliminated self-selection bias by controlling for confounding covariates such as parental education, high school GPA, and ACT scores. The major findings of the study included the following: dual enrollment participants (a) were nearly four times less likely to take remediation than non-participants, (b) earned approximately 1 extra credit hour in the first semesters of college, (c) earned higher first semester GPAs, (d) were 2.5 times more likely to graduate in 2 years (100% of degree time) and, (e) were 1.68 times more likely to graduate in 3 years (150% of degree time). The study concluded that dual enrollment benefits community college students in Tennessee, both at the beginning and completion of college. This is a significant justification for the current investment in dual enrollment by the State of Tennessee and for further increasing access to dual enrollment for all students, especially for students that live in rural areas, experience poverty, or are underrepresented in higher education.

School officials responsible for the growing international student populations struggle to find ways to help them navigate inconsistencies that may exist between federal regulations and institutional policies, and would benefit from increased understanding of ways to gain trust from diverse student populations. To determine whether student demographics might be related to propensity to trust, this study used the validated Propensity to Trust Scale (PTTS) by Frazier, Johnson, and Fainshmidt (2013), as well as a demographic questionnaire developed to measure students' background and educational attributes. Responses to an online survey from 576 international students from 71 countries were collected from a large private institution of higher education in the Western United States. Basic inferential statistics, including Analysis of Variance (ANOVA) and post hoc analysis, identified differences among demographic groups within this student population. Findings indicated that students who were not native speakers of the dominant language had a lower propensity to trust than native English speakers, and female students had a lower propensity to trust than did male students. Findings also indicated that during the senior year of school propensity to trust was significantly lower than in earlier undergraduate years and in graduate school. Implications from this study include an emphasis on the value of considering individuals within their own unique cultural and educational contexts, and avoiding a one-size-fits-all approach to fostering trust with students. Additionally, school officials should not assume that propensity to trust is consistent among those with institutional similarities and must not stereotype students based on their backgrounds.

This this three-article dissertation sought to explore the potential causal link of students’ collegiate residence with three broad categories of student outcomes. Using data from the Wabash National Study of Liberal Arts Education, each article employed propensity score matching in an effort to reduce selection bias associated with a student’s decision to live on campus. The first manuscript examined academic achievement, retention, four-year graduation, and satisfaction with the college experience and found that living on campus had no direct effect on any of these outcomes. The second manuscript explored the effect of living on campus on students’ overall health, alcohol consumption and binge drinking, smoking behaviors, exercise frequency, and psychological well-being. Findings suggest that living on campus has a positive effect on students’ first-year alcohol consumption, frequency of binge drinking, and exercising behaviors. These findings do not persist beyond the first year. Some conditional effects were uncovered, with a significant interaction between race and campus residence on some outcomes. The final study considered the effect living on campus has on student engagement. Living on campus was found to have a direct effect on positive peer interactions, frequency of interactions with student affairs staff, and co-curricular involvement. Like the second study, conditional analyses were conducted and revealed significant interactions mostly among race and campus residence.

Objective: To assess the ability of propensity score methods to maintain covariate balance and minimize bias in the estimation of treatment effect in a time-to-event setting. Data Sources: Generated simulation model Study Design: Simulation study Data Collection: 6 scenarios with varying covariate relationships to treatment and outcome with 2 different censoring prevalences Principal Findings: As time lapses, balance achieved at baseline through propensity score methods between treated and untreated groups trends toward imbalance, particularly in settings with high rates of censoring. Furthermore, there is a high degree of variability in the performance of different propensity score models with respect to effect estimation. Conclusions: Caution should be used when incorporating propensity score analysis methods in survival analyses. In these settings, if model over-parameterization is a concern, Cox regression stratified on propensity score matched pairs often provides more accurate conditional treatment effect estimates than those of unstratified matched or IPT weighted Cox regression models.

During the last decade higher education organizations and educational policy makers have substantially increased efforts to incentivize study abroad participation. These efforts are grounded in the longstanding belief that study abroad participation improves intercultural competence - an educational outcome critical in a globalized 21st century economy. Yet decades of evidence that appear to support this claim are repeatedly limited by a series of methodological weaknesses including small homogenous samples, an absence of longitudinal study design, no accounting for potential selection bias, and the lack of controls for potentially confounding demographic and college experience variables. Thus, a major competing explanation for differences found between students who do and do not study abroad continues to be the possibility that these differences existed prior to participation. The current study sought to determine the effect of study abroad on intercultural competence among 1,593 participants of the 2006 cohort of the Wabash National Study on Liberal Arts Education. The Wabash National Study is a longitudinal study of undergraduates that gathered pre- and post-test measures on numerous educational outcomes, an array of institutional and self-reported pre-college characteristics, and a host of college experiences. The current study employed both propensity score matching and covariate adjustment methods to account for pre-college characteristics, college experiences, the selection effect, and the clustered nature of the data to both cross-validate findings and provide guidance for future research. Under such rigorous analytic conditions, this study found that study abroad generated a statistically significant positive effect on intercultural competence; an effect that appears to be general rather than conditional. Moreover, both covariate adjustment and propensity score matching methods generated similar results. In examining the effect of study abroad across the three constituent subscales of the overall measure of intercultural competence, this study found that study abroad influences students' diversity of contact but has no statistically significant effect on relativistic appreciation of cultural differences or comfort with diversity. Finally, the results of this study suggest that the relationship between study abroad and intercultural competence is one of selection and accentuation, holding important implications for postsecondary policy makers, higher education institutions, and college impact scholars.

Observational studies are an indispensable complement to randomized clinical trials (RCT) for comparison of treatment effectiveness. Often RCTs cannot be carried out due to the costs of the trial, ethical questions and rarity of the outcome. When noncompliance and missing data are prevalent, RCTs become more like observational studies. The main problem is to adjust for the selection bias in the observational study. One increasingly used method is propensity-score matching. Compared to traditional multi-covariate matching methods, matching on the propensity score alleviates the curse of dimensionality. It allows investigators to balance multiple covariate distributions between treatment groups by matching on a single score. This thesis focuses on the large sample properties of the matching estimators of the treatment effect. The first part of this thesis deals with problems of the analytic supports of the logit propensity score and various matching methods. The second part of this thesis focuses on the matching estimators of additive and multiplicative treatment effects. We derive the asymptotic order of the biases and asymptotic distributions of the matching estimators. We also derive the large sample variance estimators for the treatment effect estimators. The methods and theoretical results are applied and checked in a series of simulation studies. The third part of this thesis is devoted to a comparison between propensity-score matching and multiple linear regression using simulation.

Doctor of Philosophy (PhD) / The glass-transition traverses continuously from liquid to solid behaviour, yet the role of structure in this large and gradual dynamic transition is poorly understood. This thesis presents a theoretical study of the relationship between structure and dynamics in two-dimensional glass-forming alloys, and provides new tools and real-space insight into the relationship at a microscopic level. The work is divided into two parts. Part I is concerned with the role of structure in the appearance of spatially heterogeneous dynamics in a supercooled glass-forming liquid. The isoconfigurational ensemble method is introduced as a general tool for analysing the effect that a configuration has on the subsequent particle motion, and the dynamic propensity is presented as the aspect of structural relaxation that can be directly related to microscopic variations in the structure. As the temperature is reduced, the spatial distribution of dynamic propensity becomes increasingly heterogeneous. This provides the first direct evidence that the development of spatially heterogeneous dynamics in a fragile glass-former is related to spatial variations in the structure. The individual particle motion also changes from Gaussian to non- Gaussian as the temperature is reduced, i.e. the configuration expresses its character more and more intermittently. The ability of several common measures of structure and a measure of structural ‘looseness’ to predict the spatial distribution of dynamic propensity are then tested. While the local coordination environment, local potential energy, and local free volume show some correlation with propensity, they are unable to predict its spatial variation. Simple coarse-graining does not help either. These results cast doubt on the microscopic basis of theories of the glass transition that are based purely on concepts of free volume or local potential energy. In sharp contrast, a dynamic measure of structural ‘looseness’ - an isoconfigurational single-particle Debye-Waller (DW) factor - is able to predict the spatial distribution of propensity in the supercooled liquid. This provides the first microscopic evidence for previous correlations found between short- and long-time dynamics in supercooled liquids. The spatial distribution of the DW factor changes rapidly in the supercooled liquid and suggests a picture of structural relaxation that is inconsistent with simple defect diffusion. Overall, the work presented in Part I provides a real-space description of the transition from structure-independent to structure-dependent dynamics, that is complementary to the configuration-space description provided by the energy landscape picture of the glass transition. In Part II, an investigation is presented into the effect of varying the interparticle potential on the phase behaviour of the binary soft-disc model. This represents a different approach to studying the role of structure in glass-formation, and suggests many interesting directions for future work. The structural and dynamic properties of six different systems are characterised, and some comparisons are made between them. A wide range of alloy-like structures are formed, including substitutionally ordered crystals, amorphous solids, and multiphase materials. Approximate phase diagrams show that glass-formation generally occurs between competing higher symmetry structures. This work identifies two new glass-forming systems with effective chemical ordering and substantially different short- and medium-range structure compared to the glassformer studied in Part I. These represent ideal candidates for extending the study presented in Part I. There also appears to be a close connection between quasicrystal and glass-formation in 2D via random-tiling like structures. This may help explain the experimental observation that quasicrystals sometimes vitrify on heating. The alignment of asymmetric unit cells is found to be the rate-limiting step in the crystal nucleation and growth of a substitutionally ordered crystal, and another system shows amorphous-crystal coexistence and appears highly stable to complete phase separation. The generality of these results and their implications for theoretical descriptions of the glass transition are also discussed.

<p>In this paper I study how the repeal of the Swedish wealth tax (1 of January 2007) has affected people´s labour supply behaviour. This particular issue is relevant because it may help us understand some of the effects of the earnings tax changes that have taken place in Sweden. Accoring to standard economic theory a repealed wealth tax is similar to an income effect for the persons who previously paid the tax. That means that they theoretically will want to consume more leisure, that is decrease their labour supply. The method I am using to test this hypothesis is a difference-in-difference approach where the treatment group consists of persons who previously paid the tax and the control group of comparable persons who did not pay the tax. The data I am using is taken from a Swedish database called LINDA, compiled by the Swedish Central Agency for Statistics (SCB). My main result in this paper is that the repealed wealth tax does not seem to have had any influnece on the labour supply behavior of the persons who previously paid the tax.</p>

<p>Aktivitetsgarantin är ett arbetsmarknadspolitiskt program som startades i Sverige den första augusti år 2000. I den här uppsatsen skattas aktivitetsgarantins effekt på sannolikheten att erhålla arbete. För att utvärdera den genomsnittliga effekten används en matchningsestimator eftersom programmet inte hade en experimentell utformning. De empiriska resultaten är något varierande, men ett entydigt stöd för att deltagande i aktivitetsgarantin medför ökad sannolikhet till arbete är svårt att finna. Däremot visar det sig att om arbetslösheten fortgår under åtminstone 6 månader efter samplingsperioden hittas positiva effekter av deltagande i aktivitetsgarantin.</p>

Aktivitetsgarantin är ett arbetsmarknadspolitiskt program som startades i Sverige den första augusti år 2000. I den här uppsatsen skattas aktivitetsgarantins effekt på sannolikheten att erhålla arbete. För att utvärdera den genomsnittliga effekten används en matchningsestimator eftersom programmet inte hade en experimentell utformning. De empiriska resultaten är något varierande, men ett entydigt stöd för att deltagande i aktivitetsgarantin medför ökad sannolikhet till arbete är svårt att finna. Däremot visar det sig att om arbetslösheten fortgår under åtminstone 6 månader efter samplingsperioden hittas positiva effekter av deltagande i aktivitetsgarantin.