1,720,997 research outputs found
Statistical Tests for Lyapunov Exponents of Deterministic Systems. Discussion paper No 167
No full textIn order to develop statistical tests for the Lyapunov exponents of deter-\ud
ministic dynamical systems, we develop bootstrap tests based on empirical\ud
likelihood for percentiles and expectiles of strictly stationary processes. The\ud
percentiles and expectiles are estimated in terms of asymmetric least deviations\ud
and asymmetric least squares methods. Asymptotic distributional properties of\ud
the estimators are established
Recent developments of statistical approaches in cost accounting: a review
No full textWe review and simultaneously introduce a convenient statistical concept for the mathematical representation of the Statistical Activity Cost Theory (SACT) introduced by Willett (1987 and 1988). Further, we discuss, and present a critique of, a variety of statistical models with respect to long debated accounting problems, such as the allocation of joint costs and depreciation. We finally propose that taking the effort to combine those models results in a novel statistical accounting system and this is discussed by means of the so-called virtual firm. As it has been shown that any statistical model discussed here outperforms associated deterministic counterparts, this review presents promising outcomes and useful perspectives for the accounting profession
Estimators of integrals of powers of density derivatives
No full textSimple kernel-type estimators of integrals of general powers of general derivatives of probability densities are proposed. They are based on two simple properties, and in many circumstances enjoy optimal convergence rate
A Time-Domain Test for Some Types of Non-Linearity, Discussion Paper No 168
No full textThe bispectrum and third-order moment can be viewed as equivalent tools for testing for the presence of non-linearity in stationary time series. This is because the bispectrum is the Fourier transform of the third order moment. An advantage of the bispectrum is that its estimator comprises terms which are asymptotically independent at distinct bifrequencies under the null hypothesis of linearity. An advantage of the third order moment is that its values at any subset of joint lags can be used in the test, whereas when using the bispectrum the entire (or truncated) third order moment is required to\ud
construct the Fourier transform. In this paper we propose a test for non-linearity based upon the estimated third order moment. We use the phase scrambling bootstrap method to give a non-parametric estimate of the variance of our test statistic under the null hypothesis. Using a simulation study we demonstrate that the test obtains its target significance level, with large power, when compared to an existing standard parametric test that uses the bispectrum. Further we show how the proposed test can be used to identify the source of nonlinearity due to interactions at specic frequencies. We also investigate implications for heuristic diagnosis of non-stationarity
Dependence structures in financial time series: a chaos-theoretic approach
No full textOf much interest in financial econometrics is the recovery of joint distributional behaviour of collections of contemporaneous financial time series, e.g., two related commodity price series, or two asset returns series. An approach to model their joint behaviour is to use copulae. Essentially, copulae are selected on the basis of a measure of correlation between the two series and are made to match their marginal properties. Of course, generalisations exist for more than two series. A possible limitation of this approach is that only linear correlations between series might be captured. We consider incorporating more general dependence structures, through the use of the correlation integral (as in the BDS test), as a means to refine the choice of candidate copulae in an empirical situation
Methods for estimating a conditional distribution function
Full text linkMotivated by the problem of setting prediction intervals in time series analysis, we suggest two new methods for conditional distribution estimation. The first method is based on locally fitting a logistic model and is in the spirit of recent work on locally parametric techniques in density estimation. It produces distribution estimators that may be of arbitrarily high order but nevertheless always lie between 0 and 1. The second method involves an adjusted form of the Nadaraya-Watson estimator. It preserves the bias and variance properties of a class of second-order estimators introduced by Yu and Jones but has the added advantage of always being a distribution itself. Our methods also have application outside the time series setting: fur example, to quantile estimation for independent data. This problem motivated the work of Yu and Jones
Modelling the initial pit design: the first step for project valuation
No full textOne critical factor in open pit mining projects is the estimation of the recoverable reserves. The reason for this is that at the valuation stage there is a lack of information about future metal prices and production costs. Consequently, the estimation of the recoverable reserves needs to be done based on a fixed break-even cut-off grade (BECG), in which fixed expected metal prices and production costs are assumed throughout the operating life of the mine (OLM).\ud
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In this paper, an alternative technique for estimating the recoverable reserves of an open pit mining project is presented and explained in detail. The main characteristic of this technique is that it estimates the recoverable reserves of the project using mining costs as reference: this is done due to the fact that mining costs are easier to model than metal prices. Another important characteristic of this technique is that it uses the uncertainty of the geology of the orebody, given by simulations of the deposit, to make final strategic decisions, such as the selection of the operating life of the mine and the optimal production rate, which minimise the risk of not achieving future production targets while maximising the upside potential of future rewards.\ud
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As it will be shown, the final outcome of the proposed technique is the generation of a robust open pit design, that include cutbacks and ultimate pit limits, called the marginal open pit mine design (MOPMD). One characteristic of the MOPMD is that, at each production period, it will be characterised by their respective geological uncertainty, given as probability distributions of ore, waste and metal quantities, and by marginal economical project indicators, such as cut-off grades and metal prices, among others. The details follow in the paper
Binary time series generated by chaotic logistic maps
No full textThis paper examines stochastic pairwise dependence structures in binary time series obtained from discretised versions of standard chaotic logistic maps. It is motivated by applications in communications modelling which make use of so-called chaotic binary sequences. The strength of non-linear stochastic dependence of the binary sequences is explored. In contrast to the original chaotic sequence, the binary version is non-chaotic with non-Markovian non-linear dependence, except in a special case. Marginal and joint probability distributions, and autocorrelation functions are elicited. Multivariate binary and more discretized time series from a single realisation of the logistic map are developed from the binary paradigm. Proposals for extension of the methodology to other cases of the general logistic map are developed. Finally, a brief illustration of the place of chaos-based binary processes in chaos communications is given
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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