Spurious Latent Classes in the Mixture Rasch Model     

Natalia Alexeev  Jonathan Templin  Allan S. Cohen 《Journal of Educational Measurement》2011,48(3):313-332

Mixture Rasch models have been used to study a number of psychometric issues such as goodness of fit, response strategy differences, strategy shifts, and multidimensionality. Although these models offer the potential for improving understanding of the latent variables being measured, under some conditions overextraction of latent classes may occur, potentially leading to misinterpretation of results. In this study, a mixture Rasch model was applied to data from a statewide test that was initially calibrated to conform to a 3‐parameter logistic (3PL) model. Results suggested how latent classes could be explained and also suggested that these latent classes might be due to applying a mixture Rasch model to 3PL data. To support this latter conjecture, a simulation study was presented to demonstrate how data generated to fit a one‐class 2‐parameter logistic (2PL) model required more than one class when fit with a mixture Rasch model.  相似文献   

Do altmetrics assess societal impact in a comparable way to case studies? An empirical test of the convergent validity of altmetrics based on data from the UK research excellence framework (REF)     

Lutz Bornmann  Robin Haunschild  Jonathan Adams 《Journal of Informetrics》2019,13(1):325-340

Altmetrics have been proposed as a way to assess the societal impact of research. Although altmetrics are already in use as impact or attention metrics in different contexts, it is still not clear whether they really capture or reflect societal impact. This study is based on altmetrics, citation counts, research output and case study data from the UK Research Excellence Framework (REF), and peers’ REF assessments of research output and societal impact. We investigated the convergent validity of altmetrics by using two REF datasets: publications submitted as research output (PRO) to the REF and publications referenced in case studies (PCS). Case studies, which are intended to demonstrate societal impact, should cite the most relevant research papers. We used the MHq’ indicator for assessing impact – an indicator which has been introduced for count data with many zeros. The results of the first part of the analysis show that news media as well as mentions on Facebook, in blogs, in Wikipedia, and in policy-related documents have higher MHq’ values for PCS than for PRO. Thus, the altmetric indicators seem to have convergent validity for these data. In the second part of the analysis, altmetrics have been correlated with REF reviewers’ average scores on PCS. The negative or close to zero correlations question the convergent validity of altmetrics in that context. We suggest that they may capture a different aspect of societal impact (which can be called unknown attention) to that seen by reviewers (who are interested in the causal link between research and action in society).  相似文献   

Subject-specific computer simulation model for determining elbow loading in one-handed tennis backhand groundstrokes     

King MA  Glynn JA  Mitchell SR 《Sports biomechanics / International Society of Biomechanics in Sports》2011,10(4):391-406

A subject-specific angle-driven computer model of a tennis player, combined with a forward dynamics, equipment-specific computer model of tennis ball-racket impacts, was developed to determine the effect of ball-racket impacts on loading at the elbow for one-handed backhand groundstrokes. Matching subject-specific computer simulations of a typical topspin/slice one-handed backhand groundstroke performed by an elite tennis player were done with root mean square differences between performance and matching simulations of < 0.5 degrees over a 50 ms period starting from ball impact. Simulation results suggest that for similar ball-racket impact conditions, the difference in elbow loading for a topspin and slice one-handed backhand groundstroke is relatively small. In this study, the relatively small differences in elbow loading may be due to comparable angle-time histories at the wrist and elbow joints with the major kinematic differences occurring at the shoulder. Using a subject-specific angle-driven computer model combined with a forward dynamics, equipment-specific computer model of tennis ball-racket impacts allows peak internal loading, net impulse, and shock due to ball-racket impact to be calculated which would not otherwise be possible without impractical invasive techniques. This study provides a basis for further investigation of the factors that may increase elbow loading during tennis strokes.  相似文献   

Accessibility of U.S. federal government home pages: Section 508 compliance and site accessibility statements     

Abiodun Olalere  Jonathan LazarAuthor vitae 《Government Information Quarterly》2011,28(3):303-309

U.S. federal websites are required to be accessible for people with impairments. However, despite the existing regulations and guidelines, many federal websites continue to be inaccessible, and accessibility policy statements available on federal websites often do not provide any useful information. This paper provides three contributions to the research literature: (1) an accessibility evaluation of 100 federal home pages using both human and automated methods, (2) a content analysis of existing website accessibility policy statements, and (3) a discussion of the relationship between actual Section 508 compliance and the existing accessibility policy statements on a website. The paper concludes with recommendations for improving policy related to Section 508 compliance for websites.  相似文献   

Shrink-film microfluidic education modules: Complete devices within minutes     

Nguyen D  McLane J  Lew V  Pegan J  Khine M 《Biomicrofluidics》2011,5(2):22209

As advances in microfluidics continue to make contributions to diagnostics and life sciences, broader awareness of this expanding field becomes necessary. By leveraging low-cost microfabrication techniques that require no capital equipment or infrastructure, simple, accessible, and effective educational modules can be made available for a broad range of educational needs from middle school demonstrations to college laboratory classes. These modules demonstrate key microfluidic concepts such as diffusion and separation as well as "laboratory on-chip" applications including chemical reactions and biological assays. These modules are intended to provide an interdisciplinary hands-on experience, including chip design, fabrication of functional devices, and experiments at the microscale. Consequently, students will be able to conceptualize physics at small scales, gain experience in computer-aided design and microfabrication, and perform experiments-all in the context of addressing real-world challenges by making their own lab-on-chip devices.  相似文献   

Bandpass sorting of heterogeneous cells using a single surface acoustic wave transducer pair     

Gergely Simon  Caroline Busch  Marco A. B. Andrade  Julien Reboud  Jonathan M. Cooper  Marc P. Y. Desmulliez  Mathis O. Riehle  Anne L. Bernassau 《Biomicrofluidics》2021,15(1)

Separation and sorting of biological entities (viruses, bacteria, and cells) is a critical step in any microfluidic lab-on-a-chip device. Acoustofluidics platforms have demonstrated their ability to use physical characteristics of cells to perform label-free separation. Bandpass-type sorting methods of medium-sized entities from a mixture have been presented using acoustic techniques; however, they require multiple transducers, lack support for various target populations, can be sensitive to flow variations, or have not been verified for continuous flow sorting of biological cells. To our knowledge, this paper presents the first acoustic bandpass method that overcomes all these limitations and presents an inherently reconfigurable technique with a single transducer pair for stable continuous flow sorting of blood cells. The sorting method is first demonstrated for polystyrene particles of sizes 6, 10, and 14.5 μm in diameter with measured purity and efficiency coefficients above 75 ± 6% and 85 ± 9%, respectively. The sorting strategy was further validated in the separation of red blood cells from white blood cells and 1 μm polystyrene particles with 78 ± 8% efficiency and 74 ± 6% purity, respectively, at a flow rate of at least 1 μl/min, enabling to process finger prick blood samples within minutes.  相似文献   

Designing Reading Comprehension Assessments for Reading Interventions: How a Theoretically Motivated Assessment Can Serve as an Outcome Measure     

Tenaha O’Reilly  Jonathan Weeks  John Sabatini  Laura Halderman  Jonathan Steinberg 《Educational Psychology Review》2014,26(3):403-424

When designing a reading intervention, researchers and educators face a number of challenges related to the focus, intensity, and duration of the intervention. In this paper, we argue there is another fundamental challenge—the nature of the reading outcome measures used to evaluate the intervention. Many interventions fail to demonstrate significant improvements on standardized measures of reading comprehension. Although there are a number of reasons to explain this phenomenon, an important one to consider is misalignment between the nature of the outcome assessment and the targets of the intervention. In this study, we present data on three theoretically driven summative reading assessments that were developed in consultation with a research and evaluation team conducting an intervention study. The reading intervention, Reading Apprenticeship, involved instructing teachers to use disciplinary strategies in three domains: literature, history, and science. Factor analyses and other psychometric analyses on data from over 12,000 high school students revealed the assessments had adequate reliability, moderate correlations with state reading test scores and measures of background knowledge, a large general reading factor, and some preliminary evidence for separate, smaller factors specific to each form. In this paper, we describe the empirical work that motivated the assessments, the aims of the intervention, and the process used to develop the new assessments. Implications for intervention and assessment are discussed.  相似文献   

Freedom and the Individual     

Ruth Jonathan 《Journal of Philosophy of Education》1997,31(1):109-141

  相似文献   

More Misuses of Evolutionary Psychology     

Jonathan Michael Kaplan 《Metascience》2006,15(1):177-181

  相似文献   

Online Distance Education Pedagogy: Emulating the practice of global business     

Jonathan Mark Hochberg 《Distance Education》2006,27(1):129-133

  相似文献