34 resultados para Granger causality.

em University of Queensland eSpace - Australia


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The small sample performance of Granger causality tests under different model dimensions, degree of cointegration, direction of causality, and system stability are presented. Two tests based on maximum likelihood estimation of error-correction models (LR and WALD) are compared to a Wald test based on multivariate least squares estimation of a modified VAR (MWALD). In large samples all test statistics perform well in terms of size and power. For smaller samples, the LR and WALD tests perform better than the MWALD test. Overall, the LR test outperforms the other two in terms of size and power in small samples.

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This paper examines the causal links between fertility and female labor force participation in Bangladesh over the period 1974-2000 by specifying a bivariate and several trivariate models in a vector error correction framework. The three trivariate models alternatively include average age at first marriage for females, per capita GDP and infant mortality rate, which control for the effects of other socio-economic factors on fertility and female labor force participation. All the specified models indicate an inverse long-run relationship between fertility and female labor force participation. While the bivariate model also indicates bidirectional causality, the multivariate models confirm only a unidirectional causality – from labor force participation to fertility. Further, per capita GDP and infant mortality rate appear to Granger-cause both fertility and female labor force participation.

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US President Lyndon Johnson's state visit to Australia in October 1966, came at the pinnacle of support for Australia's military involvement in the Vietnam War. Johnson's visit also occurred just weeks before an election for the House of Representatives at which the ruling Liberal-Country Party Coalition won its eighth successive, and largest victory, The proximity of these events has led many to argue that a causal relationship exists between the two. Advocates of this thesis, however, have failed to support their position with any evidence other than the anecdotal. Contrary to the assertions made by numerous political historians and observers of the period, this paper finds no evidence to support a thesis of causality. This paper argues that the Coalition's landslide victory in 1966 was both a rejection of the tired and lacklustre leadership of Labor's Arthur Calwell and a measure of the electorate's overwhelming support for Holt and his Government's policies of conscription and military involvement in Vietnam.

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Vector error-correction models (VECMs) have become increasingly important in their application to financial markets. Standard full-order VECM models assume non-zero entries in all their coefficient matrices. However, applications of VECM models to financial market data have revealed that zero entries are often a necessary part of efficient modelling. In such cases, the use of full-order VECM models may lead to incorrect inferences. Specifically, if indirect causality or Granger non-causality exists among the variables, the use of over-parameterised full-order VECM models may weaken the power of statistical inference. In this paper, it is argued that the zero–non-zero (ZNZ) patterned VECM is a more straightforward and effective means of testing for both indirect causality and Granger non-causality. For a ZNZ patterned VECM framework for time series of integrated order two, we provide a new algorithm to select cointegrating and loading vectors that can contain zero entries. Two case studies are used to demonstrate the usefulness of the algorithm in tests of purchasing power parity and a three-variable system involving the stock market.

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In this paper we develop an evolutionary kernel-based time update algorithm to recursively estimate subset discrete lag models (including fullorder models) with a forgetting factor and a constant term, using the exactwindowed case. The algorithm applies to causality detection when the true relationship occurs with a continuous or a random delay. We then demonstrate the use of the proposed evolutionary algorithm to study the monthly mutual fund data, which come from the 'CRSP Survivor-bias free US Mutual Fund Database'. The results show that the NAV is an influential player on the international stage of global bond and stock markets.

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The reconstruction of a complex scene from multiple images is a fundamental problem in the field of computer vision. Volumetric methods have proven to be a strong alternative to traditional correspondence-based methods due to their flexible visibility models. In this paper we analyse existing methods for volumetric reconstruction and identify three key properties of voxel colouring algorithms: a water-tight surface model, a monotonic carving order, and causality. We present a new Voxel Colouring algorithm which embeds all reconstructions of a scene into a single output. While modelling exact visibility for arbitrary camera locations, Embedded Voxel Colouring removes the need for a priori threshold selection present in previous work. An efficient implementation is given along with results demonstrating the advantages of posteriori threshold selection.

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This study tested hypotheses that locus of causality attributions for the academic performance of others are influenced by whether the other is a specific individual, or a typical other, and whether the other is similar or dissimilar to self. The research was carried out in two studies. Study 1 entailed development of two scales to measure perceptions of interpersonal similarity: 254 Australian undergraduates rated their similarity to either a specific other or to typical other students. In Study 2, 332 subjects completed one of the 16-item scales developed in Study 1, along with Rosenberg's self-esteem scale, and self-attribution and other-attribution versions of the Multidimensional Multi-attribution Causation Scale (MMCS). Results showed that attributions for the academic performance of others were strongly affected by whether the other was perceived to be similar or dissimilar to self, especially when the other was a specific individual. In particular, causal attributions for similar specific others were more favourable than attributions for self.

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A causally well-behaved solution of the localization problem for the free electron is given, with natural space-time transformation properties, in terms of Dirac's position operator x. It is shown that, although x is not an observable in the usual sense, and has no positive-energy (generalized) eigenstates, the four-vector density (rho(x, t), j(x, t)/c) is observable, and can be localized arbitrarily precisely about any point in space, at any instant of time, using only positive energy states. A suitable spin operator can be diagonalized at the same time.

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In this paper I offer an 'integrating account' of singular causation, where the term 'integrating' refers to the following program for analysing causation. There are two intuitions about causation, both of which face serious counterexamples when used as the basis for an analysis of causation. The 'process' intuition, which says that causes and effects are linked by concrete processes, runs into trouble with cases of misconnections', where an event which serves to prevent another fails to do so on a particular occasion and yet the two events are linked by causal processes. The chance raising intuition, according to which causes raise the chance of their effects, easily accounts for misconnections but faces the problem of chance lowering causes, a problem easily accounted for by the process approach. The integrating program attempts to provide an analysis of singular causation by synthesising the two insights, so as to solve both problems. In this paper I show that extant versions of the integrating program due to Eells, Lewis, and Menzies fail to account for the chance-lowering counterexample. I offer a new diagnosis of the chance lowering case, and use that as a basis for an integrating account of causation which does solve both cases. In doing so, I accept various assumptions of the integrating program, in particular that there are no other problems with these two approaches. As an example of the process account, I focus on the recent CQ theory of Wesley Salmon (1997).

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Objectives: To determine the relationship between pediatric assessment scores and ratings by parents and teachers regarding the amount of assistance required to complete basic activities of daily living; and to examine the relationship among scores for three commonly used pediatric assessments. Design: Prospective correlational study. 205 children with developmental disabilities. The children ranged in age from 11 to 87 mo and included 72 females and 133 males of diverse socioeconomic and ethnic backgrounds. The children were evaluated by using the Battelle Developmental Inventory Screening Test, Vineland Adaptive Behavior Scales, Functional Independence Measure for Children (WeeFIM(TM) instrument), and the Amount of Assistance Questionnaire, Results: The test-retest reliability coefficients for items on the Amount of Assistance Questionnaire were found to range from 0.82 to 0.97. Correlations among subscale scores and amount of assistance ratings were highest for the WeeFIM instrument and Battelle Developmental Inventory Screening Test. The highest correlation was between WeeFIM total rating and total amount of assistance rating (r = 0.91). Conclusion: Total WeeFIM instrument ratings and severity of disability were the best predictors of amount of assistance ratings provided by parents and teachers.

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Objective: As part of a randomised double-blind study of a new atypical antipsychotic we sought to determine both the levels of visual acuity and the occurrence of toxic side-effects in a group of patients treated for many years on a variety of antipsychotics. Method: Twenty-three inpatients with a DSM-III-R diagnosis of chronic schizophrenia from two separate hospital locations who met the criteria for the double-blind trial were examined for ocular abnormalities at both baseline and at trial completion. Results: At baseline a high prevalence of abnormalities was identified: 19 patients (82.6%) were found to have one or more ocular abnormalities, including lens opacities/cataracts and corneal pigmentation; three patients, with delusions related to the sun, were noted to have solar burns; a high proportion (almost 70%) of patients had untreated visual acuity problems. No further changes were observed at the follow-up examinations. Conclusions: The possible causes of ocular disturbance in schizophrenia and the reasons for the relatively high ocular morbidity in this group are thought to result from both illness-related factors and the effects of antipsychotic medication. Causality is confounded by a number of issues such as the high prevalence of smoking, poor general health and the variety of antipsychotic medications used in the treatment of psychosis as well as substance abuse. The clinical implications are considered in this paper in relation to the move towards community-based psychiatric services.

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This paper offers a defense of backwards in time causation models in quantum mechanics. Particular attention is given to Cramer's transactional account, which is shown to have the threefold virtue of solving the Bell problem, explaining the complex conjugate aspect of the quantum mechanical formalism, and explaining various quantum mysteries such as Schrodinger's cat. The question is therefore asked, why has this model not received more attention from physicists and philosophers? One objection given by physicists in assessing Cramer's theory was that it is not testable. This paper seeks to answer this concern by utilizing an argument that backwards causation models entail a fork theory of causal direction. From the backwards causation model together with the fork theory one can deduce empirical predictions. Finally, the objection that this strategy is questionable because of its appeal to philosophy is deflected.