Indiana University-Purdue University Indianapolis (IUPUI) / Purpose: Script concordance tests (SCTs) are assessments purported to measure clinical data interpretation. The aims of this research were to (1) test the psychometric properties of SCT items, (2) directly examine the construct validity of SCTs, and (3) explore the concurrent validity of six SCT scoring methods while also considering validity at the item difficulty and item type levels. Methods: SCT scores from a problem solving SCT (SCT-PS; n=522) and emergency medicine SCT (SCT-EM; n=1040) were used to investigate the aims of this research. An item analysis was conducted to optimize the SCT datasets, to categorize items into levels of difficulty and type, and to test for gender biases. A confirmatory factor analysis tested whether SCT scores conformed to a theorized unidimensional factor structure. Exploratory factor analyses examined the effects of six SCT scoring methods on construct validity. The concurrent validity of each scoring method was also tested via a one-way multivariate analysis of variance (MANOVA) and Pearson’s product moment correlations. Repeated measures analysis of variance (ANOVA) and one-way ANOVA tested the discriminatory power of the SCTs according to item difficulty and type. Results: Item analysis identified no gender biases. A combination of moderate model-fit indices and poor factor loadings from the confirmatory factor analysis suggested that the SCTs under investigation did not conform to a unidimensional factor structure. Exploratory factor analyses of six different scoring methods repeatedly revealed weak factor loadings, and extracted factors consistently explained only a small portion of the total variance. Results of the concurrent validity study showed that all six scoring methods discriminated between medical training levels in spite of lower reliability coefficients on 3-point scoring methods. In addition, examinees as MS4s significantly (p<0.001) outperformed their MS2 SCT scores in all difficulty categories. Cross-sectional analysis of SCT-EM data reported significant differences (p<0.001) between experienced EM physicians, EM residents, and MS4s at each level of difficulty. When considering item type, diagnostic and therapeutic items differentiated between all three training levels, while investigational items could not readily distinguish between MS4s and EM residents. Conclusions: The results of this research contest the assertion that SCTs measure a single common construct. These findings raise questions about the latent constructs measured by SCTs and challenge the overall utility of SCT scores. The outcomes of the concurrent validity study provide evidence that multiple scoring methods reasonably differentiate between medical training levels. Concurrent validity was also observed when considering item difficulty and item type.

La thématique des rayons cosmiques d'ultra-haute énergie (RCUHEs) est riche de mystères. Nous présentons l'état actuel des connaissances générales sur le sujet, ainsi que les apports et possibilités offerts par l'Observatoire Pierre Auger. Celui-ci nous a apporté plusieurs résultats majeurs dans le domaine : la mesure du spectre d'énergie au delà de quelques EeV et de la coupure à haute énergie avec une grande significativité, la mesure d'observables sensibles à la composition qui montrent un alourdissement avec l'énergie (ou une modification significative de la physique hadronique à la centaine de TeV !), et la mesure d'une anisotropie faible en dehors d'une région centrée sur une source remarquable mais pas forcément concernée, Centaurus~A. Dans la seconde partie de cette thèse, on étudie la propagation des RCUHEs depuis leur source dans le milieu extra-galactique. On étudie l'influence de la composition aux sources et des paramètres de l'accélération sur la forme des spectres à la Terre. On démontre la viabilité d'un modèle astrophysique satisfaisant, dit low-$E_{max}$, qui s'ajuste bien aux données du spectre et de la composition. Un outil numérique de propagation de protons/noyaux, notamment en présence de champs magnétiques, est également présenté dans ce cadre. Nous présenterons aussi (en quatrième partie) une étude indépendante des contraintes apportées par les données angulaires d'Auger sur la densité effective des sources de RCUHEs et leur déflexion dans les champs magnétiques. Une analyse des données par la méthode de percolation est également présentée, et démontre la faible anisotropie des données. Une partie entière est dédiée à la phénoménologie d'un messager secondaire : les photons. On expose leur propagation extra-galactique et l'outil numérique entièrement développé à ce sujet, que l'on intègre dans l'outil existant de propagation de protons/noyaux. Cette intégration aboutit à un code numérique global, véritablement multi-messagers (les neutrinos sont également traités), qui nous permet de disposer d'un outil complet, nous autorisant à fonder un modèle global de concordance capable de satisfaire l'ensemble des contraintes actuelles, dont les limites expérimentales connues sur le flux diffus de photons au TeV (par Fermi/LAT). Celui-ci est discuté dans le dernier chapitre. Nous terminons sur les perspectives offertes par la construction d'un modèle global de RCUHEs.

This thesis presents work around 3 themes: dark energy, gravitational waves and Bayesian inference. Both dark energy and gravitational wave physics are not yet well constrained. They present interesting challenges for Bayesian inference, which attempts to quantify our knowledge of the universe given our astrophysical data. A dark energy equation of state reconstruction analysis finds that the data favours the vacuum dark energy equation of state $w {=} -1$ model. Deviations from vacuum dark energy are shown to favour the super-negative ‘phantom’ dark energy regime of $w {< } -1$, but at low statistical significance. The constraining power of various datasets is quantified, finding that data constraints peak around redshift $z = 0.2$ due to baryonic acoustic oscillation and supernovae data constraints, whilst cosmic microwave background radiation and Lyman-$\alpha$ forest constraints are less significant. Specific models with a conformal time symmetry in the Friedmann equation and with an additional dark energy component are tested and shown to be competitive to the vacuum dark energy model by Bayesian model selection analysis: that they are not ruled out is believed to be largely due to poor data quality for deciding between existing models. Recent detections of gravitational waves by the LIGO collaboration enable the first gravitational wave tests of general relativity. An existing test in the literature is used and sped up significantly by a novel method developed in this thesis. The test computes posterior odds ratios, and the new method is shown to compute these accurately and efficiently. Compared to computing evidences, the method presented provides an approximate 100 times reduction in the number of likelihood calculations required to compute evidences at a given accuracy. Further testing may identify a significant advance in Bayesian model selection using nested sampling, as the method is completely general and straightforward to implement. We note that efficiency gains are not guaranteed and may be problem specific: further research is needed.

In many international schools where English is the language of learning and teaching there are large percentages of students whose first language is not English. Many of these students may have low vocabulary levels which inhibits their chances of taking full advantage of their education. Low vocabulary levels can be a particular problem for students in mainstream classes where fluent English speaking teachers are using English to teach content areas of Mathematics, Science and History. Not only do students have to comprehend the low-frequency, academic and technical vocabulary pertaining to the subject, but they also need to know the higher frequency vocabulary that makes up general English usage. If students’ vocabulary levels fall too far below the vocabulary levels with which their teachers are speaking, then their chance of comprehending the topic is small, as is their chance of succeeding in their subjects. This study has two broad aims. Firstly, I have set out to assess the English vocabulary levels of students at an international school where English is the language of learning and teaching. The majority of students at this school do not have English as their first language. The second aim of this study is to explore the vocabulary profile of the teachers’ spoken discourse at the research school. By gaining a better understanding of the nature of teacher discourse – specifically the percentage of high, mid and low-frequency vocabulary, as well as academic vocabulary that they use – English as a Second Language (ESL) teachers will be in a stronger position to identify what the vocabulary learning task is and be able to assist students in reaching the vocabulary levels necessary to make sense of their lessons. This study revealed a large gap between the generally low vocabulary levels of ESL students and the vocabulary levels spoken by their teachers. As a result the need for explicit vocabulary instruction and learning is shown to be very important in English medium (international) schools, where there are large numbers of students whose first language is not English. / Linguistics and Modern Languages / M.A. (Applied Linguistics)