63 resultados para Omitted variables


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El espacio social es un concepto ambiguo cuyo componente material está determinado por el carácter del componente social, puesto que la organización de los objetos en el espacio y el espacio mismo, responden a las normas sociales del comportamiento humano. Partimos de la premisa que los residuos generados durante el proceso de producción y del consumo tienden a tener una distribución relativamente regular en el espacio físico. La ausencia de la aleatoriedad en la dispersión de estos restos solo significa que habían sido acumulados y depositados como restos de acciones previamente planificadas no-aleatoriamente. En este trabajo planteamos estudiar la organización y la producción del espacio social de una sociedad cazadora-recolectora concreta – la sociedad yámana - a través del análisis de las actividades cotidianas que figuran en las fuentes etnográficas y en el registro arqueológico. Con este fin creamos una metodología de trabajo interdisciplinaria, basada en un enfoque etnoarqueológico, y a través del estudio de las fuentes etnográficas, los trabajos etnoarqueológicos previos y el registro arquelógico concreto, descubrimos cuáles son las posibilidades y limitaciones de este tipo de estudios. Pudimos reconocer la regularidad espacial de los procesos de producción y reproducción social y a resolver algunas preguntas acerca del estudio de la organización social en prehistoria trabajando con los datos etnoarqueológicos obtenidos en los yacimientos Lanashuaia y Túnel VII (Tierra del Fuego, Argentina), analizando el registro extraido y trabajado en varias campañas de excavaciones arqueológicas en ultimos 25 años. El presente trabajo al fondo es un experimento etnoarqueológico estándar: partiendo de la observación etnográfica registramos unas recurrencias específicas entre algunas variables (por ejemplo: mujer/lugar/tipo de trabajo), intentamos extraer las variables definitorias de esas recurrencias, y finalmente las buscamos en el espacio definido arqueológicamente.  

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Aquest treball s’ha realitzat en el Centre Educatiu Montilivi, un centre de Justícia Juvenil, on predominen les mesures en règim semiobert. L’objectiu principal del centre és oferir als menors la experiència i la formació necessària per superar els handicaps, deixar l’activitat delictiva i participar en la societat de manera normalitzada. L’any 2002 es va implantar un sistema motivacional que, basat en el condicionament operant i l’aprenentatge social, facilités la participació activa i responsable dels interns. El sistema motivacional s’estructura en etapes progressives. El menor, superat el període d’observació inicial, se l’assigna a una etapa on pot gaudir dels avantatges corresponents. Una avaluació continuada, li permetrà anar assolint la puntuació necessària que li donarà la opció de progressar a una etapa superior. En aquesta gaudirà de més avantatges. L’objectiu bàsic de la recerca és avaluar l’eficàcia del sistema motivacional pel que fa la desaparició o reducció de les conductes indesitjables de: no retorn, fugides, reincidència i conflictes dins del centre i buscar relació d’aquestes variables amb diversos factors individuals. Per dur a terme la recerca s’han seleccionat 135 menors que hem distribuït en dos grups. un grup de control anterior a la implementació del sistema motivacional; i un grup d’intervenció a qui si se’ls ha aplicat el sistema motivacional. Els resultats diuen que la mostra respon a un patró antisocial greu. També diu que l’aplicació d’un sistema motivacional no s’ha associat a una reducció de les conductes antisocials dels interns durant el període d’aplicació. Malgrat això, sí es percebut com una eina eficaç per interns i professionals.

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Aproximadament un 40% dels subjectes de la mostra de 1.14a subjectes no han arribat a ser considerats per a l’alliberament condicional, tot i haver complert les 3/4 parts de la condemna. La modalitat de llibertat condicional ordinària en complir les ¾ parts de la condemna predomina sobre la resta de modalitats d’alliberament. En el cas d’aquest estudi, només un 7,6% havia accedit al benefici de la llibertat condicional avançada. Respecte a la incidència de les variables personals en l’accés a la llibertat condicional, ser dona, tenir nacionalitat espanyola i un nivell molt baix o un nivell alt de formació influeix positivament en l’obtenció de la llibertat condicional. La variable nacionalitat estrangera té una influència molt negativa en la concessió de la llibertat condicional. Respecte a les variables penals, els delictes de lesions, seguits dels delictes contra la propietat, com tots els tipus de robatoris, tenen els percentatges de denegació de la llibertat condicional més alts. Respecte a les variables penitenciàries, es conclou que com més obert sigui el règim inicialment aplicat, més probabilitats hi ha de sortir en llibertat condicional. Les activitats realitzades durant el compliment de la condemna no semblen tenir, en general, una incidència positiva en la concessió de la llibertat condicional. En aquest sentit, es podria dir que ja a l’inici de la condemna es pot determinar les possibilitats que es tindran de sortir en llibertat condicional, independentment dels progressos o canvis que es realitzin durant el compliment de la condemna. Les variables més significatives en la concessió de la llibertat condicional, segons l’anàlisi de regressió logística, són 4: l’habitualitat, els dies totals de sortida en funció del temps, el temps passat com a preventiu i el nombre de faltes greus. La regressió logística ha permès construir una equació amb aquestes 4 variables independents, que dibuixa el perfil d’un intern en llibertat condicional, i també descriu quins són els interns susceptibles de gaudir de la llibertat condicional o no, amb la probabilitat d’encertar en 80 de cada 100 casos.

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In the last few years, many researchers have studied the presence of common dimensions of temperament in subjects with symptoms of anxiety. The aim of this study is to examine the association between temperamental dimensions (high negative affect and activity level) and anxiety problems in clinicalpreschool children. A total of 38 children, ages 3 to 6 years, from the Infant and Adolescent Mental Health Center of Girona and the Center of Diagnosis and Early Attention of Sabadell and Olot were evaluated by parents and psychologists. Their parents completed several screening scales and, subsequently, clinical child psychopathology professionals carried out diagnostic interviews with children from the sample who presented signs of anxiety. Findings showed that children with high levels of negative affect and low activity level have pronounced symptoms of anxiety. However, children with anxiety disorders do not present different temperament styles from their peers without these pathologies

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We consider the application of normal theory methods to the estimation and testing of a general type of multivariate regressionmodels with errors--in--variables, in the case where various data setsare merged into a single analysis and the observable variables deviatepossibly from normality. The various samples to be merged can differ on the set of observable variables available. We show that there is a convenient way to parameterize the model so that, despite the possiblenon--normality of the data, normal--theory methods yield correct inferencesfor the parameters of interest and for the goodness--of--fit test. Thetheory described encompasses both the functional and structural modelcases, and can be implemented using standard software for structuralequations models, such as LISREL, EQS, LISCOMP, among others. An illustration with Monte Carlo data is presented.

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In this work I study the stability of the dynamics generated by adaptivelearning processes in intertemporal economies with lagged variables. Iprove that determinacy of the steady state is a necessary condition for the convergence of the learning dynamics and I show that the reciprocal is not true characterizing the economies where convergence holds. In the case of existence of cycles I show that there is not, in general, a relationship between determinacy and convergence of the learning process to the cycle. I also analyze the expectational stability of these equilibria.

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Determining what influences mood is important for theories of emotion and research onsubjective well-being. We consider three sets of factors: activities in which people areengaged; individual differences; and incidental variables that capture when mood ismeasured, e.g., time-of-day. These three factors were investigated simultaneously in a studyinvolving 168 part-time students who each responded 30 times in an experience samplingstudy conducted over 10 working days. Respondents assessed mood on a simple bipolarscale from 1 (very negative) to 10 (very positive). Activities had significant effects but,with the possible exception of variability in the expression of mood, no systematicindividual differences were detected. Diurnal effects, similar to those already reported inthe literature, were found as was an overall Friday effect. However, these effects weresmall. Lastly, the weather had little or no influence. We conclude that simple measures ofoverall mood are not greatly affected by incidental variables.

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This paper presents findings from a study investigating a firm s ethical practices along the value chain. In so doing we attempt to better understand potential relationships between a firm s ethical stance with its customers and those of its suppliers within a supply chain and identify particular sectoral and cultural influences that might impinge on this. Drawing upon a database comprising of 667 industrial firms from 27 different countries, we found that ethical practices begin with the firm s relationship with its customers, the characteristics of which then influence the ethical stance with the firm s suppliers within the supply chain. Importantly, market structure along with some key cultural characteristics were also found to exert significant influence on the implementation of ethical policies in these firms.

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When can a single variable be more accurate in binary choice than multiple sources of information? We derive analytically the probability that a single variable (SV) will correctly predict one of two choices when both criterion and predictor are continuous variables. We further provide analogous derivations for multiple regression (MR) and equal weighting (EW) and specify the conditions under which the models differ in expected predictive ability. Key factors include variability in cue validities, intercorrelation between predictors, and the ratio of predictors to observations in MR. Theory and simulations are used to illustrate the differential effects of these factors. Results directly address why and when one-reason decision making can be more effective than analyses that use more information. We thus provide analytical backing to intriguing empirical results that, to date, have lacked theoretical justification. There are predictable conditions for which one should expect less to be more.

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Se presentan de forma resumida los resultados geoambientales obtenidos en el estudio de un término municipal motivado más por sistemática de planteamiento por parte del responsable del Plan General, que por cuestión concreta planteada sobre este ámbito en aquel término municipal. Así y todo, la información obtenida influye sobre el Plan y pone de manifiesto circunstancias qenerales que sin ser aqudas son persistentes en el tiempo, por razones obvias del ámbito terrestre, al que pertenecen

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Objective: To describe the methodology of Confirmatory Factor Analyis for categorical items and to apply this methodology to evaluate the factor structure and invariance of the WHO-Disability Assessment Schedule (WHODAS-II) questionnaire, developed by the World HealthOrganization.Methods: Data used for the analysis come from the European Study of Mental Disorders(ESEMeD), a cross-sectional interview to a representative sample of the general population of 6 european countries (n=8796). Respondents were administered a modified version of theWHODAS-II, that measures functional disability in the previous 30 days in 6 differentdimensions: Understanding and Communicating; Self-Care, Getting Around, Getting Along withOthers, Life Activities and Participation. The questionnaire includes two types of items: 22severity items (5 points likert) and 8 frequency items (continuous). An Exploratory factoranalysis (EFA) with promax rotation was conducted on a random 50% of the sample. Theremaining half of the sample was used to perform a Confirmatory Factor Analysis (CFA) inorder to compare three different models: (a) the model suggested by the results obtained in theEFA; (b) the theoretical model suggested by the WHO with 6 dimensions; (c) a reduced modelequivalent to model b where 4 of the frequency items are excluded. Moreover, a second orderfactor was also evaluated. Finally, a CFA with covariates was estimated in order to evaluatemeasurement invariance of the items between Mediterranean and non-mediterranean countries.Results: The solution that provided better results in the EFA was that containing 7 factors. Twoof the frequency items presented high factor loadings in the same factor, and one of thempresented factor loadings smaller than 0.3 with all the factors. With regard to the CFA, thereduced model (model c) presented the best goodness of fit results (CFI=0.992,TLI=0.996,RMSEA=0.024). The second order factor structure presented adequate goodness of fit (CFI=0.987,TLI=0.991, RMSEA=0.036). Measurement non-invariance was detected for one of the items of thequestionnaire (FD20 ¿ Embarrassment due to health problems).Conclusions: AFC confirmed the initial hypothesis about the factorial structure of the WHODAS-II in 6factors. The second order factor supports the existence of a global dimension of disability. The use of 4of the frequency items is not recommended in the scoring of the corresponding dimensions.

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We report on experiments aimed at comparing the hysteretic response of a Cu-Zn-Al single crystal undergoing a martensitic transition under strain-driven and stress-driven conditions. Strain-driven experiments were performed using a conventional tensile machine while a special device was designed to perform stress-driven experiments. Significant differences in the hysteresis loops were found. The strain-driven curves show reentrant behavior yield point which is not observed in the stress-driven case. The dissipated energy in the stress-driven curves is larger than in the strain-driven ones. Results from recently proposed models qualitatively agree with experiments.

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We study a class of models of correlated random networks in which vertices are characterized by hidden variables controlling the establishment of edges between pairs of vertices. We find analytical expressions for the main topological properties of these models as a function of the distribution of hidden variables and the probability of connecting vertices. The expressions obtained are checked by means of numerical simulations in a particular example. The general model is extended to describe a practical algorithm to generate random networks with an a priori specified correlation structure. We also present an extension of the class, to map nonequilibrium growing networks to networks with hidden variables that represent the time at which each vertex was introduced in the system.

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A través de la investigación presentada en este articulo se ha pretendido operacionalizar la parte predictiva de la Teoria de Acción Razonada, propuesta por Fishbein y Ajzen. Para ello, se ha utilizado la reciente metodologia de 10s modelos de ecuaciones estructurales lineales con variables latentes desarrollados por Joreskog y Sorbom, entre otros. Como dominio se ha delimitado el consumo de tabaco en distintas situaciones sociales. Después de estimar y valorar el modelo predictivo especificado desde la Teoria de Fishbein y Ajzen, se estimo y valoro el modelo generalizado propuesto por Bentler y Speckart y se asumió como mas coherente este modelo generalizado. En el trabajo también se plantean una serie de observaciones para optimizar, sobre todo, la parte metodológica de recogida de datos asociados a estos modelos y se presenta una propuesta para operacionalizar todo el sistema teórico de predicción y explicación de las conductas desde la Teoria de Fishbein y Ajzen.