Search results for "estadística"
showing 10 items of 196 documents
Testing invariance between web and paper students satisfaction surveys. A case study
2017
[EN] Purpose: This paper studied the measurement invariance (MI) across web-based and paper-based surveys to evidence if both techniques of data collection can be regarded as equivalent. Design/methodology: We develop a multigroup confirmatory factor analysis (MGCFA) with Maximum Likelihood Estimation to asses measurement invariance of the Job Diagnostic Survey (JDS) adapted to teaching, with data collected from paper and web surveys. Sample from paper surveys was constituted by 294 student of a Spanish public university in the academic years 2007-08, 2008-09 and 2009-10. Internet surveys were administered through an open source survey application called Lime Survey. We received 241 complet…
Static output-feedback control under information structure constraints
2013
An important challenge in the static output-feedback control context is to provide an isolated gain matrix possessing a zero-nonzero structure, mainly in problems presenting information structure constraints. Although some previous works have contributed some relevant results to this issue, a fully satisfactory solution has not yet been achieved up to now. In this note, by using a Linear Matrix Inequality approach and based on previous results given in the literature, we present an e cient methodology which permits to obtain an isolated static output-feedback gain matrix having, simultaneously, a zero-nonzero structure imposed a priori. Peer Reviewed
Static output-feedback controller design for vehicle suspensions: an effective two-step computational approach
2014
In this study, a novel two-step methodology is applied in designing static output-feedback controllers for a class of vehicle suspension systems. Following this approach, an effective synthesis of static output-feedback controllers can be carried out by solving two consecutive linear matrix inequality optimisation problems. To illustrate the main features of the proposed design strategy, two different static output-feedback H 8 controllers are designed for a quarter-car suspension system. The first of those controllers uses the suspension deflection and the sprung mass velocity as feedback information, whereas the second one only requires the sprung mass velocity to compute the control acti…
Static output-feedback control for vehicle suspensions: a single-step linear matrix inequality approach
2013
In this paper, a new strategy to design static output-feedback controllers for a class of vehicle suspension systems is presented. A theoretical background on recent advances in output-feedback control is first provided, which makes possible an effective synthesis of static output-feedback controllers by solving a single linear matrix inequality optimization problem. Next, a simplified model of a quarter-car suspension system is proposed, taking the ride comfort, suspension stroke, road holding ability, and control effort as the main performance criteria in the vehicle suspension design. The new approach is then used to design a static output-feedbackH∞controller that only uses the suspensi…
Manipulating the alpha level cannot cure significance testing
2018
We argue that making accept/reject decisions on scientific hypotheses, including a recent call for changing the canonical alpha level from p = 0.05 to p = 0.005, is deleterious for the finding of new discoveries and the progress of science. Given that blanket and variable alpha levels both are problematic, it is sensible to dispense with significance testing altogether. There are alternatives that address study design and sample size much more directly than significance testing does; but none of the statistical tools should be taken as the new magic method giving clear-cut mechanical answers. Inference should not be based on single studies at all, but on cumulative evidence from multiple in…
Experimental demonstration of bistable phase locking in a photorefractive oscillator
2012
We report experimental evidence of bistable phase locking in nonlinear optics, in particular, in a photorefractive oscillator emitting in few transverse modes. Bistable phase locking is a recently proposed method for converting a laserlike system, which is phase invariant, into a phase-bistable one by injecting a suitable spatially modulated monochromatic beam, resonant with the laser emission, into the optical cavity. We experimentally demonstrate that the emission on the fundamental TEM00 mode becomes phase bistable by injection of a beam with the shape of the TEM10 mode with appropriate frequency, in accordance with recent theoretical predictions [K. Staliunas et al., Phys. Rev. A 80, 02…
Characterization of the optical properties at the ANTARES site using the Optical Beacon system. Influence on the detector performance
2014
Neutrino Astronomy aims to scientifically exploit neutrinos as a new cosmic messenger to explore high energy astrophysical phenomena in the TeV-PeV energy range. The very low fluxes and the small interaction crosssection of neutrinos with matter require the construction of massive detectors. When the incoming neutrino direction can be reconstructed with a reasonable angular accuracy, the detector is dubbed "telescope", since the neutrinos, having no electric charge, point back to their source. In the Cherenkov technique, the observation of the neutrino is carried out through the detection of the Cherenkov light induced by the charged relativistic particles produced in the neutrino interacti…
Research Letter: is neuroticism a risk factor for postpartum depression?
2012
Although the relationship between personality and depressive illness is complex (Shea, 2005), there is empirical evidence that some personality features such as neuroticism, harm avoidance, introversion, dependency, self-criticism or perfectionism are related to depressive illness risk (Gunderson et al. 1999). Moreover, personality traits, especially neuroticism, may explain the increased prevalence of depression among females (Goodwin & Gotlib, 2004). Few studies have explored neuroticism, extraversion and psychoticism as risk factors for depression after an event as stressful as childbirth. Pitt (1968) was the first author to report high scores on neuroticism and low scores on extraversio…
Distribuciones previas objetivas para el modelo Dirichlet-multinomial: una aplicación en la agricultura
2015
La chufa, Cyperus sculentus, es un tubérculo que se utiliza principalmente para la elaboración de horchata. Se cultiva en la comarca de l'Horta Nord, en Valencia, y tiene una gran importancia socioeconómica en la zona. La mancha negra en los tubérculos de chufa es una enfermedad de origen desconocido, que produce un ennegrecimiento de la piel que conlleva a su depreciación comercial, pues un cierto porcentaje de tubérculos deben ser desechados para su venta. El objetivo de este trabajo es analizar si la selección de tubérculos sin mancha negra, para su utilización como simiente, supone una mejora en la cosecha en cuanto a una menor incidencia de la enfermedad. Los datos analizados proceden …
Uso secuencial de herramientas de control de calidad en procesos productivos: una aplicación en el sector agroalimentario = Sequential use of quality…
2014
<p>Las diferentes herramientas del Control Estadístico de Calidad proporcionan mejores resultados si su uso se lleva a cabo de manera secuencial, facilitando la detección de los puntos débiles del proceso productivo. Así, en el presente estudio se expone un método de trabajo en el que se utilizan, atendiendo a la necesidad en cada punto de la cadena de producción, algunas de dichas herramientas. Concretamente se propone el uso del diagrama de flujo, gráfico de Pareto, hojas de comprobación, gráficos de control (en este caso gráfico p y gráfico de media-recorrido), así como el análisis de la varianza (ANOVA). El procedimiento se aplica a una empresa del sector agroalimentario, interesa…