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31.
Influence diagnostics in the capital asset pricing model under elliptical distributions 总被引:1,自引:0,他引:1
In this paper we consider the Capital Asset Pricing Model under Elliptical (symmetric) Distributions. This class of distributions, which contains the normal distribution, t, contaminated normal and power exponential, among others, offers a more flexible framework for modelling asset prices or returns. In order to analyze the sensibility to possible outliers and/or atypical returns of the maximum likelihood estimators, the local influence method was implemented. The results are illustrated by using a set of shares from companies who trade in the Chilean Stock Market. Our main conclusion is that symmetric distributions having heavier tails than those of the normal distribution, especially the t distribution with small degrees of freedom, show a better fit and allow the reduction of the influence of atypical returns in the maximum likelihood estimators. 相似文献
32.
Anne-Laure Boulesteix Robert Hable Sabine Lauer Manuel J. A. Eugster 《The American statistician》2015,69(3):201-212
In computational sciences, including computational statistics, machine learning, and bioinformatics, it is often claimed in articles presenting new supervised learning methods that the new method performs better than existing methods on real data, for instance in terms of error rate. However, these claims are often not based on proper statistical tests and, even if such tests are performed, the tested hypothesis is not clearly defined and poor attention is devoted to the Type I and Type II errors. In the present article, we aim to fill this gap by providing a proper statistical framework for hypothesis tests that compare the performances of supervised learning methods based on several real datasets with unknown underlying distributions. After giving a statistical interpretation of ad hoc tests commonly performed by computational researchers, we devote special attention to power issues and outline a simple method of determining the number of datasets to be included in a comparison study to reach an adequate power. These methods are illustrated through three comparison studies from the literature and an exemplary benchmarking study using gene expression microarray data. All our results can be reproduced using R codes and datasets available from the companion website http://www.ibe.med.uni-muenchen.de/organisation/mitarbeiter/020_professuren/boulesteix/compstud2013. 相似文献
33.
Nicolas Loewe Mehdi Bagherzadeh Luis Araya-Castillo Claudio Thieme Joan Manuel Batista-Foguet 《Social indicators research》2014,118(1):71-86
This article examines the subjective antecedents of life satisfaction of workers. Adopting a ‘bottom-up’ perspective, we assessed the unique influence that satisfaction with multiple life domains have on evaluative judgments of overall life satisfaction. Based on a nationwide sample of 530 Chilean workers, we simultaneously tested the effects of seven life domain satisfactions that have been consistently included in extant models of life satisfaction and subjective well-being. These were satisfaction with health, financial situation, social relationships, one’s self-worth, leisure-time, family, and work. Having controlled for age and gender, results showed that satisfaction with one’s financial situation was the dominant predictor of overall life satisfaction of workers, with a weight of .36. Satisfaction with family, work, and health had effects of .25, .14, and .14, respectively. Interestingly, satisfaction with one’s self-worth, leisure-time, and social relationships did not have statistically significant effects on life satisfaction, although the first two showed t values near the critical value. 相似文献
34.
Hartigan (1975) defines the number q of clusters in a d ‐variate statistical population as the number of connected components of the set {f > c}, where f denotes the underlying density function on Rd and c is a given constant. Some usual cluster algorithms treat q as an input which must be given in advance. The authors propose a method for estimating this parameter which is based on the computation of the number of connected components of an estimate of {f > c}. This set estimator is constructed as a union of balls with centres at an appropriate subsample which is selected via a nonparametric density estimator of f. The asymptotic behaviour of the proposed method is analyzed. A simulation study and an example with real data are also included. 相似文献
35.
In this paper the periodic integer-valued autoregressive model of order one with period T, driven by a periodic sequence of independent Poisson-distributed random variables, is studied in some detail. Basic probabilistic and statistical properties of this model are discussed. Moreover, parameter estimation is also addressed. Specifically, the methods of estimation under analysis are the method of moments, least squares-type and likelihood-based ones. Their performance is compared through a simulation study. 相似文献
36.
Armando Serrano‐Lombillo Ignacio Escuder‐Bueno Manuel G. de Membrillera‐Ortuño Luis Altarejos‐García 《Risk analysis》2011,31(6):1000-1015
In the past few years, the field of dam safety has approached risk informed methodologies throughout the world and several methodologies and programs are appearing to aid in the systematization of the calculations. The most common way of implementing these calculations is through the use of event trees, computing event probabilities, and incremental consequences. This methodology is flexible enough for several situations, but its generalization to the case of systems of several dams is complex and its implementation in a completely general calculation methodology presents some problems. Retaining the event tree framework, a new methodology is proposed to calculate incremental risks. The main advantage of this proposed methodology is the ease with which it can be applied to systems of several dams: with a single risk model that describes the complete system and with a single calculation the incremental risks of the system can be obtained, being able to allocate the risk of each dam and of each failure mode. The article shows how both methodologies are equivalent and also applies them to a case study. 相似文献
37.
Juan Manuel Moreno-Manso M José Godoy-MerinoÁngel Suárez-Muñoz M Elena García-Baamonde 《Children and youth services review》2013
This work analyses the communicative competence and the factors that facilitate and perturb the socialisation of immigrant students in primary education. It provides greater knowledge concerning the relationship between the immigrant student's social and linguistic competence. It also analyses the presence of difficulties in the different language components (morphology, syntax, semantics and pragmatics). The sample is made up of a total of 326 immigrant students between 6 and 12 years of age, attending 10 different schools. The study demonstrates that immigrant students possess a low level of linguistic dominion. All the linguistic components analysed are affected, although greater difficulties are evident in morphology and syntax than in semantics and pragmatics. The relationship between linguistic competence and the factors that facilitate and perturb socialisation is underlined. This work concludes that there is a significant relation between semantics and pragmatics and several socialisation factors (leadership, aggressiveness–stubbornness and anxiety–shyness). The educational centres should be aware of the complicated learning process that immigrant students have to go through. 相似文献
38.
In this paper we consider testing that an economic time series follows a martingale difference process. The martingale difference hypothesis has typically been tested using information contained in the second moments of a process, that is, using test statistics based on the sample autocovariances or periodograms. Tests based on these statistics are inconsistent since they cannot detect nonlinear alternatives. In this paper we consider tests that detect linear and nonlinear alternatives. Given that the asymptotic distributions of the considered tests statistics depend on the data generating process, we propose to implement the tests using a modified wild bootstrap procedure. The paper theoretically justifies the proposed tests and examines their finite sample behavior by means of Monte Carlo experiments. 相似文献
39.
Summary and Conclusions A case can be made that labor unions are seeking to gain control of the financial leverage of employee pension funds as a
means of offsetting a secular decline in membership which has occurred over the past twenty years and which has been accelerating.
Pension fund assets are now substantial and are growing very rapidly so that even partial or indirect influence over investment
policies could have major impacts on the economy. Unions have already achieved success on a limited scale with the pension
fund weapon. Their intention to achieve widespread influence through this vehicle is signalled by the establishment in January,
1981, of a monthly newsletter,Labor & Investments which is devoted exclusively to the union use of employee pension funds.
In sum, it is clear that the union use of employee pension funds is a very timely and significant topic. The papers that follow
may not provide definitive answers to the many questions produced by this new initiative, but they do enhance our understanding
of the issues involved. 相似文献
40.
The minimum and maximum order statistics from many of the common bivariate exponential distributions are predominantly generalized mixtures of exponentials; however, the maximum from the Friday and Patil bivariate exponential (FPBVE) model is either a generalized mixture of three or fewer exponentials or a generalized mixture of gamma and exponentials. In this article, we obtain conditions based on the weights and parameters of the generalized mixtures of gamma and one or two exponential distributions that yield legitimate probability models. Furthermore, we analyze properties of the failure rate of the maximum from the FPBVE model. This answers a question raised in Baggs and Nagaraja (1996). 相似文献