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Análisis comparativo de estimadores pretest de heterocedasticidad en modelos econométricos. Un estudio Monte Carlo.

Rafaela Dios Palomares, C. Rodríguez Fonseca (1999)

Qüestiió

En el presente artículo se recogen los resultados de una investigación llevada a cabo sobre el comportamiento de pretest de heterocedasticidad. Con este fin se ha diseñado un experimento Monte Carlo, introduciendo como proceso generador de datos un modelo con tres supuestos sobre la estructura de la varianza del error y con distintos niveles de heteroscedasticidad para cada uno de ellos. Asimismo, se analiza la potencia de los diferentes contrastes de heterocedasticidad bajo los distintos supuestos...

Assessing influence in survival data with a cured fraction and covariates.

Edwin M. M. Ortega, Vicente G. Cancho, Victor Hugo Lachos (2008)

SORT

Diagnostic methods have been an important tool in regression analysis to detect anomalies, such as departures from error assumptions and the presence of outliers and influential observations with the fitted models. Assuming censored data, we considered a classical analysis and Bayesian analysis assuming no informative priors for the parameters of the model with a cure fraction. A Bayesian approach was considered by using Markov Chain Monte Carlo Methods with Metropolis-Hasting algorithms steps to...

El modelo lineal sin término independiente y el coeficiente de determinación. Un estudio Monte Carlo.

Rafaela Dios Palomares (1998)

Qüestiió

En el presente trabajo se analiza y compara mediante un experimento Monte Carlo el comportamiento de cinco expresiones para el Coeficiente de Determinación cuando el modelo lineal se especifica sin término independiente. Se ensayan distintos valores del parámetro poblacional P2, que mide la proporción de varianza explicada por el modelo, introduciendo también la multicolinealidad como factor de variación en el diseño. Se confirma el coeficiente propuesto por Heijmans y Neudecker (1987) y el de Barten...

El sesgo condicionado en el análisis de influencia: una revisión.

Juan Manuel Muñoz Pichardo, Juan Luis Moreno Rebollo, M. Teresa Gómez Gómez, Alicia Enguix González (2001)

Qüestiió

El sesgo condicionado se ha propuesto como diagnóstico de influencia en distintos modelos y técnicas estadísticas. Tratando de recoger una visión global de la utilidad del concepto, en este trabajo se hace una revisión general del mismo relacionándolo con la curva de sensibilidad y la curva de influencia muestral. Además, se señalan posibles líneas de trabajo que permitirán abordar el análisis de la influencia a través de este enfoque en una gran variedad de técnicas estadísticas.

Graphical display in outlier diagnostics; adequacy and robustness.

Nethal K. Jajo (2005)

SORT

Outlier robust diagnostics (graphically) using Robustly Studentized Robust Residuals (RSRR) and Partial Robustly Studentized Robust Residuals (PRSRR) are established. One problem with some robust residual plots is that the residuals retain information from certain predicated values (Velilla, 1998). The RSRR and PRSRR techniques are unaffected by this complication and as a result they provide more interpretable results.

Influence diagnostics in exponentiated-Weibull regression models with censored data.

Edwin M. M. Ortega, Vicente G. Cancho, Heleno Bolfarine (2006)

SORT

Diagnostic methods have been an important tool in regression analysis to detect anomalies, such as departures from the error assumptions and the presence of outliers and influential observations with the fitted models. The literature provides plenty of approaches for detecting outlying or influential observations in data sets. In this paper, we follow the local influence approach (Cook 1986) in detecting influential observations with exponentiated-Weibull regression models. The relevance of the...

Linear model with inaccurate variance components

Lubomír Kubáček (1996)

Applications of Mathematics

A linear model with approximate variance components is considered. Differences among approximate and actual values of variance components influence the proper position and the shape of confidence ellipsoids, the level of statistical tests and their power function. A procedure how to recognize whether these diferences can be neglected is given in the paper.

Outliers in models with constraints

Lubomír Kubáček (2006)

Kybernetika

Outliers in univariate and multivariate regression models with constraints are under consideration. The covariance matrix is assumed either to be known or to be known only partially.

Sensitivity analysis in linear models

Shuangzhe Liu, Tiefeng Ma, Yonghui Liu (2016)

Special Matrices

In this work, we consider the general linear model or its variants with the ordinary least squares, generalised least squares or restricted least squares estimators of the regression coefficients and variance. We propose a newly unified set of definitions for local sensitivity for both situations, one for the estimators of the regression coefficients, and the other for the estimators of the variance. Based on these definitions, we present the estimators’ sensitivity results.We include brief remarks...

Some Diagnostic Tools in Robust Econometrics

Jan Kalina (2011)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

Highly robust statistical and econometric methods have been developed not only as a diagnostic tool for standard methods, but they can be also used as self-standing methods for valid inference. Therefore the robust methods need to be equipped by their own diagnostic tools. This paper describes diagnostics for robust estimation of parameters in two econometric models derived from the linear regression. Both methods are special cases of the generalized method of moments estimator based on implicit...

Strange Design Points in Linear Regression

Andrej Pázman (2011)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

We discuss, partly on examples, several intuitively unexpected results in a standard linear regression model. We demonstrate that direct observations of the regression curve at a given point can not be substituted by observations at two very close neighboring points. On the opposite, we show that observations at two distant design points improve the variance of the estimator. In an experiment with correlated observations we show somewhat unexpected conditions under which a design point gives no...

The Type A Uncertainty

Lubomír Kubáček, Eva Tesaříková (2011)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

If in the model of measurement except useful parameters, which are to be determined, other auxiliary parameters occur as well, which were estimated from another experiment, then the type A and B uncertainties of measurement results must be taken into account. The type A uncertainty is caused by the new experiment and the type B uncertainty characterizes an accuracy of the parameters which must be used in estimation of useful parameters. The problem is to estimate of the type A uncertainty in the...

Trimmed Estimators in Regression Framework

TomĂĄĹĄ Jurczyk (2011)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

From the practical point of view the regression analysis and its Least Squares method is clearly one of the most used techniques of statistics. Unfortunately, if there is some problem present in the data (for example contamination), classical methods are not longer suitable. A lot of methods have been proposed to overcome these problematic situations. In this contribution we focus on special kind of methods based on trimming. There exist several approaches which use trimming off part of the observations,...

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