Conditional tests for elliptical symmetry using robust estimators

This paper presents a procedure for testing the hypothesis that the underlying distribution of the data is elliptical when using robust location and scatter estimators instead of the sample mean and covariance matrix. Under mild assumptions that include elliptical distributions without first moments, we derive the test statistic asymptotic behaviour under the null hypothesis and under special alternatives. Numerical experiments allow to compare the behaviour of the tests based on the sample mean and covariance matrix with that based on robust estimators, under various elliptical distributions and different alternatives. This comparison was done looking not only at the observed level and power but we rather use the size-corrected relative exact power which provides a tool to assess the test statistic skill to detect alternatives. We also provide a numerical comparison with other competing tests.Comment: In press in Communications in Statistics: Theory and Methods, 201

Financial Markets in Times of Stress

In this paper, we examine which markets are most synchronized internationally and exhibit the greater extent of comovement. We focus on daily data for four asset markets: bonds, equities, foreign exchange, and domestic money market. Our sample covers thirty-five developed and emerging market countries during 1997-1999. The extent of comovement and responsiveness to external shocks is examined in different ways. To measure the response of these markets to adverse external shocks, we date the peaks in domestic interest rates and bond spreads and the largest daily declines in equity prices and assess the extent of clustering around the same period. We also analyze which markets show evidence of greatest comovement in general, irrespective of whether there are adverse shocks or not.

Leading indicators of currency crises

The authors examine the empirical evidence on currency crises and propose a specific early-warning system. This system involves monitoring the evolution of several indicators that tend to exhibit unusual behavior in the periods preceding a crisis. An indicator exceeding a certain threshold value should be interpreted as a warning"signal"that a currency crisis may take place within the following 24 months. The threshold values are calculated to strike a balance between the risk of having many false signals and the risk of missing many crises. Within this approach, the variables with the best track record include exports, deviations of the real exchange rate from trend, the ratio of broad money to gross international reserves, output, and equity prices. The evidence does not support some of the other indicators that were considered, including imports, bank deposits,the difference between foreign and domestic real deposit interest rates, and the ratio of lending to deposit interest rates.Payment Systems&Infrastructure,Economic Theory&Research,Fiscal&Monetary Policy,Environmental Economics&Policies,Labor Policies,Economic Theory&Research,Macroeconomic Management,Economic Stabilization,Environmental Economics&Policies,Financial Economics

The Influence of Participation in the Healthy Choices Program for Community Dwelling Individuals with Serious Mental Illness

Due to the prevalence of serious mental illness, both nationally and statewide, creation of sufficient community-based services that focus on mental and physical health would help to meet a need for a comprehensive approach to mental health care treatment and quality of life (QoL). With the creation of the Healthy Choices program the principal investigator (PI) examined how participationin a community-based healthy living program affects perception of QoL in individuals with serious mental illness. The HealthyChoices program is a community-based program that assists participants with serious mental illness to make healthy lifestyle choices. Although perception of QoL has been previously measured in populations with serious mental illness, it is essential to evaluate this perception as an outcome that stems from participation in a community-based healthy living program. The purpose of this study is to evaluate the impact of participation in the Healthy Choices program on perception of QoL on theparticipants of the program. A mixed methods approach to data collection was implemented for this study. The Wisconsin Quality of Life Index (WQLI) client questionnaire and the World Health Organization Disability Assessment Schedule (WHODAS) was administered to subjects who participated in the Healthy Choices program along with Mental Wellness groups (HCMW) and subjects who only participated in Mental Wellness workshops (MW-only). Qualitative data was collected via administration of a structured interview questionnaire and was administered to both groups. Quantitative findings were not significant in supporting that participation in the Healthy Choices program improved perception ofQoL and level of disability. However, qualitative findings were significant in supporting that participants in the Healthy Choicesprogram developed a perception of satisfaction in terms of physical and mental health and ability to make healthier lifestyles choices. The Healthy Choices participants also perceived that making lifestyle choices, that promoted physical and mental health, assisted them in feeling less physically and psychologically disabled

¿La actitud hacia la matemática influye en el rendimiento académico?

Este trabajo tiene por objetivo mostrar los resultados obtenidos en una investigación realizada durante el ciclo lectivo 2008, respecto de la Actitud Hacia la Matemática (AHM) y su influencia en el Rendimiento Académico de los alumnos en el examen de Ingreso a la Facultad Regional Tucumán de la UTN y en la asignatura Álgebra y Geometría Analítica perteneciente al primer año de la Carrera de Ingeniería en Sistemas de Información. La metodología utilizada es la propia de un diseño exploratorio descriptivo y la investigación realizada es no experimental de corte transversal. Se utilizó la escala tipo Thurstone, adaptada al contexto, para medir el grado de AHM de los estudiantes. Estos resultados permitieron concluir que la AHM es relevante para el rendimiento académico de los alumnos. Por lo tanto, es necesario que los docentes evaluemos las percepciones de los estudiantes sobre su desempeño académico para descubrir intereses y realizar innovaciones metodológicas que optimicen el proceso educativo

Technological properties of milks fermented with thermophilic lactic acid bacteria at suboptimal temperature

In the present work the synergistic relationship between different strains of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus was studied at optimal (44°C) and suboptimal temperatures (30°C). Acidification, viscosity, whey syneresis, and bacterial concentration of the final product were evaluated on single-strain and mixed cultures after 24 h at 30°C and 6 h at 44°C. Three pairs of strains (LBB+CP2, LBP+CP2, and LBR+CP2) showed synergistic effect, which was reflected by the viscosity and syneresis of the coagulum. These results were more significant when cultures were incubated at 30°C, reaching apparent viscosity values of 19 to 28 mPa × s. On the other hand, lactobacilli cultures enhanced the growth of two streptococci strains (CP2 and CP4). These results were confirmed by cultures of streptococci supplemented with supernatants of culture of lactobacilli. Those supernatants stimulate the viscosity produced by CP2 and CP4 strains and reduce the syneresis of all cultures of streptococci. Neither the increase of viscosity nor reduction of syneresis could be attributed to a decrease of pH.Centro de Investigación y Desarrollo en Criotecnología de Alimento