Skill set profile clustering based on student capability vectors computed from online tutoring data

In educational research, a fundamental goal is identifying which skills students have mastered, which skills they have not, and which skills they are in the process of mastering. As the number of examinees, items, and skills increases, the estimation of even simple cognitive diagnosis models becomes difficult. To address this, we introduce a capability matrix showing for each skill the proportion correct on all items tried by each student involving that skill. We apply variations of common clustering methods to this matrix and discuss conditioning on sparse subspaces. We demonstrate the feasibility and scalability of our method on several simulated datasets and illustrate the difficulties inherent in real data using a subset of online mathematics tutor data. We also comment on the interpretability and application of the results for teachers

Skill set profile clustering: the empty K-means algorithm with automatic specification of starting cluster centers

While students’ skill set profiles can be estimated with formal cognitive diagnosis models [8], their computational complexity makes simpler proxy skill estimates attractive [1, 4, 6]. These estimates can be clustered to generate groups of similar students. Often hierarchical agglomerative clustering or k-means clustering is utilized, requiring, for K skills, the specification of 2^K clusters. The number of skill set profiles/clusters can quickly become computationally intractable. Moreover, not all profiles may be present in the population. We present a flexible version of k-means that allows for empty clusters. We also specify a method to determine efficient starting centers based on the Q-matrix. Combining the two substantially improves the clustering results and allows for analysis of data sets previously thought impossible

Coping styles associated with post-traumatic stress and depression symptoms following childbirth in croatian women

Childbirth is a normative event in a woman's life and is considered as a positive event. However, one in three women perceive childbirth as a physical threat to themselves or their new-born and 3% of women develop posttraumatic stress disorder (PTSD) following childbirth. Poor coping strategies have been associated with PTSD following childbirth. However, previous studies mainly utilised unidimensional measures of coping strategies, therefore, it remains to be investigated which specific dimensions of coping are more predictive of PTSD after childbirth. The aims of this study were to explore whether women in Croatia report PTSD symptoms following childbirth, and how different coping styles were related to PTSD and depression symptoms. Women (N = 160) who gave birth in the last two years, completed an online questionnaire measuring PTSD symptoms (Impact of Event Scale – IES), postnatal depression symptoms (Edinburgh Postnatal Depression Scale – EPDS) and coping styles (Brief Cope). In this sample, 1.9% reported severe PTSD symptoms following childbirth and 21.9% reported depression symptoms. Many women (66.7%) with PTSD symptoms reported depression symptoms. On the other hand, 28.6% of women with depression symptoms also reported PTSD symptoms, showing that there is a higher co-morbidity of PTSD and depression than vice versa. Avoidant coping styles, specifically, denial and self-blame were positively correlated with both PTSD and depression symptoms. Moreover, of avoidant coping styles, behavioural disengagement was positively correlated with PTSD symptoms only, while self-distraction was positively correlated with depression symptoms only. Also, lower levels of planning and higher levels of emotional support were related to higher levels of depression. However, after controlling for postnatal psychopathology symptoms, coping styles were not significant predictors of PTSD symptoms, but self-blame was a significant predictor of depression symptoms. Psychopathological symptoms following childbirth are reported by Croatian women and are related to coping styles. The avoidant coping style, self-blame, is particularly associated with depression symptoms. Future studies should explore predictors of postpartum PTSD in Croatian women in more representative samples during pregnancy and with the follow-up after childbirth. Also, screening for postnatal psychopathological symptoms should be performed both for depression and PTSD symptoms

A single-board preprocessor and pulse generator

The Aeronomy Lab. of NOAA has designed and built a single board, programmable radar controller for use with VHF ST (stratosphere troposphere) radars. The controller consists of a coherent integrator preprocessor and a radar pulse generator, both of which are described, as well as interfaces to an antenna beam switch and a receiver bandwidth switch. The controller occupies a single slot in a Data General Nova of Eclipse computer. The integrator and pulse generator take advantage of high density, dual port FIFO chips such as the 512 x 9 Mostek MK 4501. These FIFOs have separate input and output ports and independent read and write cycles with cycle times of less than 200 ns, making them very fast and easy to interface. A simple block diagram of the coherent integrator is shown. The integrator is designed to handle inputs from one receiver (2 channels) with 1 sec sample spacing. The pulse generator is based on controllers designed by R. F. Woodman for the Arecibo and SOUSY radars us a recirculating memory scheme

The colossal vitality of his illusion : the myth of the American dream in the modern American novel

This dissertation argues that the American dream is a large-scale cultural myth, and that through an analysis of the dream’s mythic structure we can locate a paradigm according to which both American literature and American culture are organized. The American dream has maintained unique relevance across the historical, regional, and cultural diversity of the American nation, in part because it always remains abstract and resists firm definition. Nevertheless, by breaking the broad myth into its most basic elemental parts we can begin to see patterns across the many distinctive versions of the American dream, such that we can identify the American dream as a generic category. This project therefore proceeds by analyzing the most basic narrative features of the American dream: its actor or hero, its setting or universe, and its primary action. Through an analysis of the figure of the self-made man, the “frontier” as American spatial metaphor, and the action of upward mobility, this dissertation locates common features across myriad versions of this American dream myth in order to establish the American dream as a pervasive organizing ideal within American culture. This dissertation focuses its study on American fiction of the twentieth century, where the American dream finds its clearest articulations, and it has special recourse to nineteenth-century and early American history and culture as the ground for this modern sense of the American dream. Finally, I end with a discussion of American literature of the last decade, in which I discuss prevalent contemporary attitudes about the American dream in order to assess its current condition. Ultimately, this dissertation suggests that the American dream, because it is a genuine cultural myth, both organizes American cultural experience and structures American literature about that experience

A Research Proposal: How can the United States Postal Service Respond and Recover From a Decade of Decline?

The purpose of this proposal is to identify the various financial struggles the United States Postal Service is currently facing. The interpretation of the related literature reveals some of the issues which the Postal Service is currently facing. Through the analysis of articles addressing the present and past volumes of mail and the recent usage of postal facilities it is evident that there is still a need for the USPS to survive. This proposal examines the current actions taken to save the United States Postal Service from their financial turmoil and also presents the results of past actions. It is evident that more serious action needs to be taken along with help from Congress in order to address the numerous issues. Proposed are the assessment of attitudes and needs towards the USPS from households, small and large businesses, and postal employees themselves, while also assessing the current level of service that is required from the USPS. The various researches identify the continuous downward spiral in which the United States Postal Service has fallen. The Method section provides potential data collection and analysis procedures for the assessment

Post-traumatic stress during pregnancy and the postpartum period

Research on PTSD in pregnancy and postpartum is relatively new but clearly demonstrates the importance of recognising and treating women with PTSD at this time. Women with PTSD in pregnancy are at greater risk of pregnancy complications and health behaviours that have a negative impact on the woman and fetus. In addition, approximately 1 to 3% of women develop PTSD as a direct response to the events of birth; and rates are increased in high risk groups such as women who have preterm or stillborn infants or life-threatening complications during pregnancy or labour. Models of the etiology of postpartum PTSD focus on the interaction between individual vulnerability, risk, and protective factors during and after birth. To date, there is strongest evidence for the role of previous psychiatric problems, a history of trauma, severe complications during birth, support, and women’s subjective experience of birth in postpartum PTSD. Very little research has examined screening or intervention, although intervention is possible at many levels. Midwife debriefing is commonly provided in the UK but there is inconsistent evidence of its efficacy. Further research is therefore desperately needed and we highlight key research topics that need addressing