A mixture of experts model for rank data with applications in election studies

A voting bloc is defined to be a group of voters who have similar voting preferences. The cleavage of the Irish electorate into voting blocs is of interest. Irish elections employ a ``single transferable vote'' electoral system; under this system voters rank some or all of the electoral candidates in order of preference. These rank votes provide a rich source of preference information from which inferences about the composition of the electorate may be drawn. Additionally, the influence of social factors or covariates on the electorate composition is of interest. A mixture of experts model is a mixture model in which the model parameters are functions of covariates. A mixture of experts model for rank data is developed to provide a model-based method to cluster Irish voters into voting blocs, to examine the influence of social factors on this clustering and to examine the characteristic preferences of the voting blocs. The Benter model for rank data is employed as the family of component densities within the mixture of experts model; generalized linear model theory is employed to model the influence of covariates on the mixing proportions. Model fitting is achieved via a hybrid of the EM and MM algorithms. An example of the methodology is illustrated by examining an Irish presidential election. The existence of voting blocs in the electorate is established and it is determined that age and government satisfaction levels are important factors in influencing voting in this election.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS178 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Enhancing student communication skills via debating engineering ethics

In Engineering, the construction of informed, persuasive and convincing arguments is at the very core of everyday practice. However, in taught postgraduate education there is often an excessive focus on assessment of these skills through written arguments or oral presentations that are usually in the form of long uninterrupted monologues, where the construction of the arguments themselves is almost never challenged. To change this status quo, we have successfully pioneered the use of oral debate as a dynamic and engaging mechanism to develop and assess this skill in our Chemical Engineering MSc students. Debate is an ideal mechanism to assess our students’ ability to construct arguments as it actively encourages them to (1) think about both sides of an argument, (2) consider how they can persuade others and (3) express their viewpoint professionally but with conviction. For this reason, the debates undertaken were linked to important engineering ethical dilemmas, by discussing topics such as “should developing countries prioritise the shift to clean energy over economic growth”. The development of this debate-based training and assessment has had numerous positive outcomes on the students’ learning experience and vital skills development. Importantly students found the debates to be both an interesting and enjoyable method of assessment and noted that the skills learned would be useful in their future careers. In this concept paper we present our experiences in delivering debate assessments to engineering students along with recommendations for practitioners wishing to implement similar styles of performative assessments in their own pedagogy

Slow-Speed Supernovae from the Palomar Transient Factory: Two Channels

Since the discovery of the unusual prototype SN 2002cx, the eponymous class of low-velocity, hydrogen-poor supernovae has grown to include at most another two dozen members identified from several heterogeneous surveys, in some cases ambiguously. Here we present the results of a systematic study of 1077 hydrogen-poor supernovae discovered by the Palomar Transient Factory, leading to nine new members of this peculiar class. Moreover we find there are two distinct subclasses based on their spectroscopic, photometric, and host galaxy properties: The "SN 2002cx-like" supernovae tend to be in later-type or more irregular hosts, have more varied and generally dimmer luminosities, have longer rise times, and lack a Ti II trough when compared to the "SN 2002es-like" supernovae. None of our objects show helium, and we counter a previous claim of two such events. We also find that these transients comprise 5.6+17-3.7% (90% confidence) of all SNe Ia, lower compared to earlier estimates. Combining our objects with the literature sample, we propose that these subclasses have two distinct physical origins.Comment: 49 pages, 36 figures, submitted to Ap

Mixed membership models for rank data: Investigating structure in Irish voting data

A mixed membership model is an individual level mixture model where individuals have partial membership of the profiles (or groups) that characterize a population. A mixed membership model for rank data is outlined and illustrated through the analysis of voting in the 2002 Irish general election. This particular election uses a voting system called proportional representation using a single transferable vote (PR-STV) where voters rank some or all of the candidates in order of preference. The data set considered consists of all votes in a constituency from the 2002 Irish general election. Interest lies in highlighting distinct voting profiles within the electorate and studying how voters affiliate themselves to these voting profiles. The mixed membership model for rank data is fitted to the voting data and is shown to give a concise and highly interpretable explanation of voting patterns in this election

Reaching the summit of discharge summaries: a quality improvement project

Background Discharge summaries need to be completed in a timely manner, to improve communication between primary and secondary care, and evidence suggests that delays in discharge summary completion can lead to patient harm. Following a hospital health and safety review due to the sheer backlog of notes in the doctor’s room and wards, urgent action had to be undertaken to improve the discharge summary completion process at our hospital’s paediatric assessment unit. It was felt that the process would best be carried out within a quality improvement (QI) project. Methods Kotter’s ‘eight-step model for change’ was implemented in this QI project with the aim to clear the existing backlog of pending discharge summaries and improve the timeliness of discharge summary completion from the hospital’s paediatric assessment unit. A minimum target of 10% improvement in the completion rate of discharge summaries was set as the primary goal of the project. Results Following the implementation of the QI processes, we were able to clear the backlog of discharge summaries within 9 months. We improved completion within 24 hours, from <10% to 84%, within 2 months. The success of our project lies in the sustainability of the change process; to date we have consistently achieved the target completion rates since the inception of the project. As a result of the project, we were able to modify the junior doctor rota to remove discharge summary duty slots and bolster workforce on the shop floor. This is still evident in November 2020, with consistently improved discharge summary rates. Conclusion QI projects when conducted successfully can be used to improve patient care, as well as reduce administrative burden on junior doctors. Our QI project is an example of how Kotter’s eight-step model for change can be applied to clinical practice

Star cluster population of high mass black hole mergers in gravitational wave data

Stellar evolution theories predict a gap in the black hole birth mass spectrum as the result of pair instability processes in the cores of massive stars. This gap, however, is not seen in the binary black hole masses inferred from gravitational wave data. One explanation is that black holes form dynamically in dense star clusters where smaller black holes merge to form more massive black holes, populating the mass gap. We show that this model predicts a distribution of the effective and precessing spin parameters, and , within the mass gap that is insensitive to assumptions about black hole natal spins and other astrophysical parameters. We analyze the distribution of as a function of primary mass for the black hole binaries in the third gravitational wave transient catalog. We infer the presence of a high mass and isotropically spinning population of black holes that is consistent with hierarchical formation in dense star clusters and a pair-instability mass gap with a lower edge at . We compute a Bayes factor relative to models that do not allow for a high mass population with a distinct distribution. Upcoming data will enable us to tightly constrain the hierarchical formation hypothesis and refine our understanding of binary black hole formation

Using Minecraft to engage children with science at public events

Engagement with science and scientific skills is an important aspect of children's ability to navigate the world around them, but engagement with science is low in comparison with other subjects. The Lancaster University outreach project Science Hunters takes a novel approach to engaging children with environmental science research through a constructivist pedagogical approach using the popular computer game Minecraft. While Minecraft is extensively used in formal education settings, few data are available on its use in public engagement with scientific research, and the relationship between children's and adults' attitudes to science and computer games are complex. Through motivational surveys conducted as part of the project evaluation, we analysed feedback from participants who attended sessions as part of a programme at public events, to explore the basic demographics of children attending our events, and whether it is the prospect of learning about science, or the opportunity to play Minecraft that leads them to choose our activity. We also present evaluation of general feedback from participants at public events over four years to give a broader view of participants' response to the activities