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A
Caeiro, F., & Gomes D. S. R. P. (2015).  Adaptive estimation of a tail shape second order parameter. International Conference of Computational Methods in Sciences and Engineering 2015 (ICCMSE 2015). , 2015/12/31: American Institute of Physics Inc. Abstract

In Statistics of Extremes, the tail shape second order parameter is a relevant parameter whenever we want to improve the estimation of first order parameters. We shall consider two semi-parametric estimators of the shape second order parameter, parameterized with a tuning parameter. We provide a Monte Carlo comparative simulation study of several algorithms for the choice of such tuning parameter and for an adaptive estimation of the shape second order parameter.In Statistics of Extremes, the tail shape second order parameter is a relevant parameter whenever we want to improve the estimation of first order parameters. We shall consider two semi-parametric estimators of the shape second order parameter, parameterized with a tuning parameter. We provide a Monte Carlo comparative simulation study of several algorithms for the choice of such tuning parameter and for an adaptive estimation of the shape second order parameter.

Lita da Silva, J., Caeiro F., Natário I., & Braumann C. A. (2013).  Advances in Regression, Survival Analysis, Extreme Values, Markov Processes and Other Statistical Applications. , Berlin Heidelberg: Springerproductflyer_978-3-642-34903-4.pdf
Caeiro, F., Gomes M. I., & Pestana D. (2009).  Alguns resultados adicionais sobre a variância de um estimador de viés reduzido do índice de cauda.. (Oliveira, I., Correia, E., Ferreira, F. Dias, S. e Braumann, C., Ed.).Actas do XVI Congresso Anual da Sociedade Portuguesa de Estatística - "Arte de Explicar o Acaso".. Abstract2009spe_art016.pdf

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F., C., Gomes, & M.I. (2013).  Asymptotic Comparison at Optimal Levels of Minimum-Variance Reduced-Bias Tail-Index Estimators. Advances in Regression, Survival Analysis, Extreme Values, Markov Processes and Other Statistical Applications. 83-91., Jan: Springer Berlin Heidelberg Abstract
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Caeiro, F., & Gomes M. I. (2010).  An asymptotically unbiased moment estimator of a negative extreme value index.. Discuss. Math., Probab. Stat.. 30, 5-19., Number 1 Abstract

{Summary: We consider a new class of consistent semi-parametric estimators of a negative extreme value index, based on the set of the $k$ largest observations. This class of estimators depends on a control or tuning parameter, which enables us to have access to an estimator with a null second-order component of asymptotic bias, and with a rather interesting mean squared error, as a function of $k$. We study the consistency and asymptotic normality of the proposed estimators. Their finite sample behaviour is obtained through Monte Carlo simulation.}

B
Caeiro, F., & Gomes I. M. (2015).  Bias reduction in the estimation of a shape second-order parameter of a heavy-tailed model. Journal Of Statistical Computation And SimulationJournal Of Statistical Computation And Simulation. 85(17), 3405 - 3419., 2015 AbstractWebsite

In extreme value theory, the shape second-order parameter is a quite relevant parameter related to the speed of convergence of maximum values, linearly normalized, towards its limit law. The adequate estimation of this parameter is vital for improving the estimation of the extreme value index, the primary parameter in statistics of extremes. In this article, we consider a recent class of semi-parametric estimators of the shape second-order parameter for heavy right-tailed models. These estimators, based on the largest order statistics, depend on a real tuning parameter, which makes them highly flexible and possibly unbiased for several underlying models. In this article, we are interested in the adaptive choice of such tuning parameter and the number of top order statistics used in the estimation procedure. The performance of the methodology for the adaptive choice of parameters is evaluated through a Monte Carlo simulation study.In extreme value theory, the shape second-order parameter is a quite relevant parameter related to the speed of convergence of maximum values, linearly normalized, towards its limit law. The adequate estimation of this parameter is vital for improving the estimation of the extreme value index, the primary parameter in statistics of extremes. In this article, we consider a recent class of semi-parametric estimators of the shape second-order parameter for heavy right-tailed models. These estimators, based on the largest order statistics, depend on a real tuning parameter, which makes them highly flexible and possibly unbiased for several underlying models. In this article, we are interested in the adaptive choice of such tuning parameter and the number of top order statistics used in the estimation procedure. The performance of the methodology for the adaptive choice of parameters is evaluated through a Monte Carlo simulation study.

Caeiro, F., & Gomes I. M. (2002).  Bias reduction in the estimation of parameters of rare events.. Theory of Stochastic Processes. 8(24), 67-76. Abstract2002tsp_caeiro_gomes.pdf

{Consider the distribution function $EV_{\gamma}(x)=\exp(-(1+\gamma x)^{- 1/\gamma}),\ \gamma>0,\ 1+\gamma x>0$, to which $\max(X_{1},łdots, X_{n})$ is attracted after suitable linear normalization. The authors consider the underlying model $F$ in the max-domain of attraction of $EV_{\gamma}$, where $ X_{i:n},\ 1łeq Iłeq n$, denotes the i-th ascending order statistic associated to the random sample $(X_{1},łdots, X_{n})$ from the unknown distribution function $F$. This article is devoted to studying semi-parametric estimators of $\gamma$ in the form $$\gamma_{n}^{(þeta,\alpha)}(k)=(\Gamma(\alpha)/M_{n}^{(\alpha- 1)}(k))łeft(M_{n}^{(þeta\alpha)}(k)/\Gamma(þeta\alpha+1)\right) ^{1/þeta},\quad \alpha\geq 1,\quad þeta>0,$$ parametrized by the parameters $\alpha$ and $þeta$, which may be controlled, where $M_{n}^{(0)}=1$ and $ M_{n}^{(\alpha)}(k)=k^{-1}\sum_{i=1}^{k}(łn X_{n-i+1:n}-łn X_{n-k:n})^{\alpha}$, $\alpha>0$, is a consistent estimator of $\Gamma(\alpha+1)\gamma^{\alpha}$, as $k\toınfty$, and $k=o(n)$, as $n\toınfty$.\par The authors derive the asymptotic distributional properties of the considered class of estimators and obtain that for $þeta>1$ it is always possible to find a control parameter $\alpha$ which makes the dominant component of the asymptotic bias of the proposed estimator null and depends on the second order parameter $\rho$. An investigation of the $\rho$-estimator is presented.}

Gomes, M. I., Caeiro F., & Figueiredo F. (2004).  Bias reduction of a tail index estimator through an external estimation of the second-order parameter.. Statistics. 38, 497-510., Number 6 Abstract

{Summary: We first consider a class of consistent semi-parametric estimators of a positive tail index $\gamma$, parametrised in a tuning or control parameter $\alpha$. Such a control parameter enables us to have access for any available sample, to an estimator of the tail index $\gamma$ with a null dominant component of asymptotic bias and consequently with a reasonably flat mean squared error pattern, as a function of $k$, the number of top-order statistics considered.\par Such a control parameter depends on a second-order parameter $\rho$, which will be adequately estimated so that we may achieve a high efficiency relative to the classical Hill estimator [ıt B. M. Hill}, Ann. Stat. 3, 1163–1174 (1975; Zbl 0323.62033)] provided we use a number of top-order statistics larger than the one usually required for the estimation through the Hill estimator. An illustration of the behaviour of the estimators is provided, through the analysis of the daily log-returns on the Euro-US\$ exchange rates.}

Gomes, I. M., Caeiro F., Henriques-Rodrigues L., & Manjunath B. g (2016).  Bootstrap Methods in Statistics of Extremes. Extreme Events in Finance. 117 - 138., 2016/10/7: John Wiley & Sons, Inc. Abstract
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C
Caeiro, F., & Gomes M. I. (2008).  Caudas pesadas: t de Student e variante assimétrica versus metodologia semi-paramétrica.. Actas do XV Congresso Anual da Sociedade Portuguesa de Estatística - “Da Teoria à Prática”. 127-136., Lisboaart053.pdf
Caeiro, F., & Gomes I. M. (2002).  A class of asymptotically unbiased semi-parametric estimators of the tail index.. Test. 11, 345-364., Number 2 Abstract

{Summary: We consider a class of consistent semi-parametric estimators of a positive tail index $\gamma$, parameterized by a tuning or control parameter $\alpha$. Such a control parameter enables us to have access, for any available sample, to an estimator of $\gamma$ with a null dominant component of asymptotic bias, and with a reasonably flat mean squared error pattern, as a function of $k$, the number of top order statistics considered. Moreover, we are able to achieve a high efficiency relative to the classical Hill estimator [ıt B. M. Hill}, Ann. Stat. 3, 1163–1174 (1975; Zbl 0323.62033)], provided we may have access to a larger number of top order statistics than the number needed for optimal estimation through the Hill estimator.}

F., C., & M.I. G. (2013).  A Class of Semi-parametric Probability Weighted Moment Estimators. Recent Developments in Modeling and Applications in Statistics. 139-147., Jan: Springer Berlin Heidelberg Abstract
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Caeiro, F., Mateus A., & Soltane L. (2021).  A class of weighted Hill estimators. Computational and Mathematical Methods. , may: Wiley AbstractWebsite
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Ayana, F., & Frederico C. (2013).  Comparing several tests of randomness based on the difference of observations. 809-812., Jan, Number 1558 Abstract

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Mateus, A., & Caeiro F. (2022).  Confidence Intervals for the Shape Parameter of a Pareto Distribution. AIP Conference Proceedings. 2425, Abstract
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Gomes, M. I., Caeiro F., Figueiredo F., Henriques-Rodrigues L., & Pestana D. (2020).  Corrected-Hill versus partially reduced-bias value-at-risk estimation. Communications in Statistics: Simulation and Computation. 49, 867-885., Number 4 Abstract
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Penalva, H., Ivette Gomes M., Caeiro F., & Manuela Neves M. (2020).  A couple of non reduced bias generalized means in extreme value theory: An asymptotic comparison. Revstat Statistical Journal. 18, 281-298., Number 3 Abstract
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D
Mateus, A. M. X. F., & Caeiro F. A. G. G. (2015).  The difference-sign randomness test. NTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2015. 1702, , 2015: American Institute of Physics Inc. Abstract

In this paper we review the properties of the difference-sign randomness test. First we analyse the exact andasymptotic distribution of the test statistic and provide a table with values for the exact distribution function, for samples ofsize n ≤ 32. Then, we also present several moments of the statistic test, under the null hypothesis of randomness and underthe hypothesis of the existence of a linear trend. Finally, we present an illustration of the test difference-sign to a real data set.In this paper we review the properties of the difference-sign randomness test. First we analyse the exact andasymptotic distribution of the test statistic and provide a table with values for the exact distribution function, for samples ofsize n ≤ 32. Then, we also present several moments of the statistic test, under the null hypothesis of randomness and underthe hypothesis of the existence of a linear trend. Finally, we present an illustration of the test difference-sign to a real data set.

Caeiro, F., Gomes M. I., & Pestana D. (2005).  Direct reduction of bias of the classical Hill estimator.. REVSTAT. 3, 113-136., Number 2 Abstract

{Summary: We are interested in an adequate estimation of the dominant component of the bias of ıt B. M. Hill}\,'s estimator [Ann. Stat. 3, 1163–1174 (1975; Zbl 0323.62033)] of a positive tail index $\gamma$, in order to remove it from the classical Hill estimator in different asymptotically equivalent ways. If the second order parameters in the bias are computed at an adequate level $k_1$ of a larger order than that of the level $k$ at which the Hill estimator is computed, there may be no change in the asymptotic variances of these reduced bias tail index estimators, which are kept equal to the asymptotic variance of the Hill estimator, i.e., equal to $\gamma^2$. The asymptotic distributional properties of the proposed estimators of $\gamma$ are derived and the estimators are compared not only asymptotically, but also for finite samples through Monte Carlo techniques.}

E
Gomes, M. I., & Caeiro F. (2014).  Eficiency of partially reduced-bias mean-of-order-p versus minimum-variance reduced-bias extreme value index estimation. COMPSTAT 2014: 21th International Conference on Computational Statistics. 289-298., Jan, Geneve Abstractgomes_caeiro_compstat2014_reprint.pdf

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Caeiro, F., & Mateus A. (2018).  Empirical Power Study of the Jackson Exponentiality Test. Demography and Health Issues. 225–235.: Springer International Publishing Abstract
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Caeiro, F., & Gomes M. I. (2006).  Estimação de quantis elevados em estatística de extremos. Actas do XIII Congresso Anual da Sociedade Portuguesa de Estatística - "Ciência Estatística". 217-228.2006spe217-228.pdf
Mateus, A., & Caeiro F. (2018).  Exact and Approximate Probabilities for the Null Distribution of Bartels Randomness Test. Contributions to Statistics. 227–240.: Springer International Publishing Abstract
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