Differential item functioning via robust scaling

This paper proposes a new method for assessing differential item functioning (DIF) in item response theory (IRT) models. The method does not require pre-specification of anchor items, which is its main virtue. It is developed in two main steps, first by showing how DIF can be re-formulated as a problem of outlier detection in IRT-based scaling, then tackling the latter using established methods from robust statistics. The proposal is a redescending M-estimator of IRT scaling parameters that is tuned to flag items with DIF at the desired asymptotic Type I Error rate during estimation. Theoretical results guarantee that the method performs reasonably well when fewer than one-half of the items on a test exhibit DIF. Data simulations show that the proposed method compares favorably to currently available approaches, and a real data example illustrates its application in a research context where pre-specification of anchor items is infeasible. The focus of the paper is the two-parameter logistic model in two independent groups, with extensions to other settings considered in the conclusion.Comment: 28 pages, 5 figure

Yang-Lee Theory for a Nonequilibrium Phase Transition

To analyze phase transitions in a nonequilibrium system we study its grand canonical partition function as a function of complex fugacity. Real and positive roots of the partition function mark phase transitions. This behavior, first found by Yang and Lee under general conditions for equilibrium systems, can also be applied to nonequilibrium phase transitions. We consider a one-dimensional diffusion model with periodic boundary conditions. Depending on the diffusion rates, we find real and positive roots and can distinguish two regions of analyticity, which can identified with two different phases. In a region of the parameter space both of these phases coexist. The condensation point can be computed with high accuracy.Comment: 4 pages, accepted for publication in Phys.Rev.Let

Genome Sequence Conservation of Hendra Virus Isolates during Spillover to Horses, Australia

Bat-to-horse transmission of Hendra virus has occurred at least 14 times. Although clinical signs in horses have differed, genome sequencing has demonstrated little variation among the isolates. Our sequencing of 5 isolates from recent Hendra virus outbreaks in horses found no correlation between sequences and time or geographic location of outbreaks

Complexidade e escala na investigação da eficácia do ensino: reflexões do estudo MET

Researchers and policymakers in the US and beyond increasingly seek to identify teaching qualities that are associated with academic achievement gains for K-12 students through effectiveness studies. Yet teaching quality varies with academic content and social contexts, involves multiple participants, and requires a range of skills, knowledge, and dispositions. In this essay, we address the inescapable tension between complexity and scale in research on teaching effectiveness. We provide five recommendations to study designers and analysts to manage this tension to enhance effectiveness research, drawing on our recent experiences as the first external analysts of the Measures of Effective Teaching (MET) study. Our recommendations address conceptual framing, the measurement of teaching (e.g., observation protocols, student surveys), sampling, classroom videoing, and the use and interpretation of value-added models.Investigadores y legisladores en los Estados Unidos y en otros países buscan identificar las cualidades de la enseñanza que se asocian con incrementos de desempeño académico para alumnos de primaria y secundaria a través de estudios de eficacia. Sin embargo, la calidad de la enseñanza varía según el contenido académico y los contextos sociales, involucra a múltiples participantes y requiere una variedad de habilidades, conocimientos y disposiciones. En este ensayo, abordamos la ineludible tensión entre la complejidad y la escala en la investigación sobre la eficacia de la enseñanza. Proveemos cinco recomendaciones a los diseñadores de estudios y analistas para manejar esta tensión y mejorar la investigación de eficacia, aprovechando nuestras experiencias recientes como los primeros analistas externos del estudio Measures of Effective Teaching (MET). Nuestras recomendaciones abordan el marco conceptual, la medición de la enseñanza (por ej., protocolos de observación, encuestas de estudiantes), el muestreo, el video en el aula y el uso e interpretación de modelos de valor agregado.Pesquisadores e legisladores nos Estados Unidos e em outros países buscam identificar as qualidades de ensino associadas ao aumento do desempenho acadêmico de alunos do ensino fundamental e médio por meio de estudos de eficácia. No entanto, a qualidade do ensino varia de acordo com o conteúdo acadêmico e os contextos sociais, envolve múltiplos participantes e requer uma variedade de habilidades, conhecimentos e disposições. Neste ensaio, abordamos a tensão inescapável entre complexidade e escala na pesquisa sobre a eficácia do ensino. Fornecemos cinco recomendações para projetistas e analistas de estudo para gerenciar essa tensão e melhorar a pesquisa sobre eficácia, alavancando nossas experiências recentes como os primeiros analistas externos do estudo Measures of Effective Teaching (MET). Nossas recomendações abordam a estrutura conceitual, a medição do ensino (por exemplo, protocolos de observação, pesquisas com estudantes), amostragem, vídeo em sala de aula e o uso e interpretação de modelos de valor agregado

Comparative Responses in Lung Function Measurements with Tiotropium in Adolescents and Adults, and Across Asthma Severities:A Post Hoc Analysis

INTRODUCTION: Airway obstruction is usually assessed by measuring forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and peak expiratory flow (PEF). This post hoc study investigated comparative responses of lung function measurements in adults and adolescents (full analysis set, N = 3873) following treatment with tiotropium Respimat®. METHODS: Lung function outcomes were analysed from five phase III trials in adults (≥ 18 years) with symptomatic severe, moderate and mild asthma (PrimoTinA-asthma®, MezzoTinA-asthma® and GraziaTinA-asthma®, respectively), and one phase III trial in adolescents (12-17 years) with symptomatic moderate asthma (RubaTinA-asthma®). Changes from baseline versus placebo in FEV1, FVC, PEF and FEV1/FVC ratio with tiotropium 5 µg or 2.5 µg added to at least stable inhaled corticosteroids at week 24 (week 12 in GraziaTinA-asthma) were analysed. RESULTS: All lung function measures improved in all studies with tiotropium 5 µg (mean change from baseline versus placebo), including peak FEV1 (110-185 mL), peak FVC (57-95 mL) and morning PEF (15.8-25.6 L/min). Changes in adolescents were smaller than those in adults, and were statistically significant primarily for FEV1 and PEF, but not for FVC. CONCLUSION: Consistent improvements were seen across all lung function measures with the addition of tiotropium to other asthma treatments in adults across all severities, whereas the improvements with tiotropium in adolescents primarily impacted measures of flow rather than lung volume. This may reflect less pronounced airway remodelling and air trapping in adolescents with asthma versus adults

Hendra Virus Outbreak with Novel Clinical Features, Australia

To determine the epidemiologic and clinical features of a 2008 outbreak of Hendra virus infection in a veterinary clinic in Australia, we investigated the equine case-series. Four of 5 infected horses died, as did 1 of 2 infected staff members. Clinical manifestation in horses was predominantly neurologic. Preclinical transmission appears likely

Henipavirus Infection in Fruit Bats (Pteropus giganteus), India

We tested 41 bats for antibodies against Nipah and Hendra viruses to determine whether henipaviruses circulate in pteropid fruit bats (Pteropus giganteus) in northern India. Twenty bats were seropositive for Nipah virus, which suggests circulation in this species, thereby extending the known distribution of henipaviruses in Asia westward by >1,000 km

InforMing the PAthway of COPD Treatment (IMPACT) Trial: Fibrinogen Levels Predict Risk of Moderate or Severe Exacerbations

Background: Fibrinogen is the frst qualifed prognostic/predictive biomarker for exacerbations in patients with chronic obstructive pulmonary disease (COPD). The IMPACT trial investigated futicasone furoate/umeclidinium/ vilanterol (FF/UMEC/VI) triple therapy versus FF/VI and UMEC/VI in patients with symptomatic COPD at risk of exacer‑ bations. This analysis used IMPACT trial data to examine the relationship between fbrinogen levels and exacerbation outcomes in patients with COPD. Methods: 8094 patients with a fbrinogen assessment at Week 16 were included, baseline fbrinogen data were not measured. Post hoc analyses were performed by fbrinogen quartiles and by 3.5 g/L threshold. Endpoints included on-treatment exacerbations and adverse events of special interest (AESIs). Results: Rates of moderate, moderate/severe, and severe exacerbations were higher in the highest versus lowest fibrinogen quartile (0.75, 0.92 and 0.15 vs 0.67, 0.79 and 0.10, respectively). The rate ratios (95% confidence interval [CI]) for exacerbations in patients with fibrinogen levels ≥ 3.5 g/L versus those with fibrinogen levels \u3c 3.5 g/L were 1.03 (0.95, 1.11) for moderate exacerbations, 1.08 (1.00, 1.15) for moderate/severe exacerbations, and 1.30 (1.10, 1.54) for severe exacerbations. There was an increased risk of moderate/severe exacerbation (hazard ratio [95% CI]: highest vs lowest quartile 1.16 [1.04, 1.228]; ≥ 3.5 g/L vs \u3c 3.5 g/L: 1.09 [1.00, 1.16]) and severe exacerbation (1.35 [1.09, 1.69]; 1.27 [1.08, 1.47], respectively) with increasing fibrinogen level. Cardiovascular AESIs were highest in patients in the highest fibrinogen quartile. Conclusions: Rate and risk of exacerbations was higher in patients with higher fbrinogen levels. This supports the validity of fbrinogen as a predictive biomarker for COPD exacerbations, and highlights the potential use of fbrinogen as an enrichment strategy in trials examining exacerbation outcomes