Sample Kurtosis, GARCH-t and the Degrees of Freedom Issue

Econometric modeling based on the Student’s t distribution introduces an additional parameter — the degree of freedom. In this paper we use a simulation study to investigate the ability of (i) the GARCH-t model (Bollerslev, 1987) to estimate the true degree of freedom parameter and (ii) the sample kurtosis coefficient to accurately determine the implied degrees of freedom. Simulation results reveal that the GARCH-t model and the sample kurtosis coefficient provide biased and inconsistent estimates of the degree of freedom parameter. Moreover, by varying ó2, we find that only the constant term in the conditional variance equation is affected, while the other parameters remain unaffected.Student’s t distribution, Degree of freedom, Kurtosis coefficient, GARCH t model

Testing for Structural Breaks and other forms of Non-stationarity: a Misspecification Perspective

In the 1980s and 1990s the issue of non-stationarity in economic time series has been in the context of unit roots vs. mean trends in AR(p) models. More recently this perspective has been extended to include structural breaks. In this paper we take a much broader perspective by viewing the problem as one of misspecification testing: assessing the stationarity of the underlying process. The proposed misspecification testing procedure relies on resampling techniques to enhance the informational content of the observed data in an attempt to capture heterogeneity `locally' using rolling window estimators of the primary moments of the stochastic process. The effectiveness of the testing procedure is assessed using extensive Monte Carlo simulationsMaximum Entropy Bootstrap, Non-Stationarity

Conditional Cash Transfers and Schooling Decisions: Evidence from Urban Mexico

Using administrative data from the urban Mexican Oportunidades program, this paper analyzes why poor households choose less education for their children, even when offered financial compensation for school attendance. Each school year, half of recipients forgo income for which they are eligible by failing to send children to school. Using a random effects probit and fractional response model, the analysis provides strong evidence that the poorest households, those with more dependents and high school students, recipients with limited education, and those living in large urban areas are less likely to have their children attend school and thus receive partial payments

Neural correlates of pain acceptance and the role of the cerebellum:Functional connectivity and anatomical differences in individuals with headaches versus matched controls

Background: Despite functional connectivity network dysfunction among indi-viduals with headaches, no studies have examined functional connectivity neuralcorrelates and anatomical differences in coping with headaches.Methods: This study investigated inter-individual variability in whole-brainfunctional connectivity and anatomical differences among 37 individuals withprimary headaches and 24 age- and gender-matched controls, and neural cor-relates of psychological flexibility (PF) that was previously found to contributeto headache adjustment. Participants (84% women; M headache severity = 4/10;M age = 43 years) underwent functional magnetic resonance imaging scans andcompleted questionnaires to examine global and subnetwork brain areas, andtheir relations with PF components, controlling for age, gender, education, andhead- motion.Results: Seed and voxel-based contrast analyses between groups showed atypicalfunctional connectivity of regions involved in pain matrix and core resting-statenetworks. Pain acceptance was the sole PF component that correlated with thecerebellum (x, y, z: 28, −72, −34, p-false discovery rate <0.001), where individualswith headaches showed higher grey matter density compared to controls.Conclusions: The cerebellum, recently implicated in modulating emotional andcognitive processes, was indicated to process information resembling what indi-viduals do when practicing pain acceptance. Our findings establish for the firsttime this connection of the cerebellum and its role in pain acceptance. We pro-pose that pain acceptance might be a behavioural biomarker target that couldmodulate problematic headache perceptions and brain networks abnormalities

Family physicians\u27 professional identity formation: a study protocol to explore impression management processes in institutional academic contexts.

BACKGROUND: Despite significant differences in terms of medical training and health care context, the phenomenon of medical students\u27 declining interest in family medicine has been well documented in North America and in many other developed countries as well. As part of a research program on family physicians\u27 professional identity formation initiated in 2007, the purpose of the present investigation is to examine in-depth how family physicians construct their professional image in academic contexts; in other words, this study will allow us to identify and understand the processes whereby family physicians with an academic appointment seek to control the ideas others form about them as a professional group, i.e. impression management. METHODS/DESIGN: The methodology consists of a multiple case study embedded in the perspective of institutional theory. Four international cases from Canada, France, Ireland and Spain will be conducted; the \u22case\u22 is the medical school. Four levels of analysis will be considered: individual family physicians, interpersonal relationships, family physician professional group, and organization (medical school). Individual interviews and focus groups with academic family physicians will constitute the main technique for data generation, which will be complemented with a variety of documentary sources. Discourse techniques, more particularly rhetorical analysis, will be used to analyze the data gathered. Within- and cross-case analysis will then be performed. DISCUSSION: This empirical study is strongly grounded in theory and will contribute to the scant body of literature on family physicians\u27 professional identity formation processes in medical schools. Findings will potentially have important implications for the practice of family medicine, medical education and health and educational policies

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Search for stop and higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top-quark (stop) and the Higgs boson (higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 inverse femtobarns of proton-proton collision data at sqrt(s) = 8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the stop mass below 360 to 410 GeV, depending on the higgsino mass

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good