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101.
Minimax estimation of a binomial probability under LINEX loss function is considered. It is shown that no equalizer estimator
is available in the statistical decision problem under consideration. It is pointed out that the problem can be solved by
determining the Bayes estimator with respect to a least favorable distribution having finite support. In this situation, the
optimal estimator and the least favorable distribution can be determined only by using numerical methods. Some properties
of the minimax estimators and the corresponding least favorable prior distributions are provided depending on the parameters
of the loss function. The properties presented are exploited in computing the minimax estimators and the least favorable distributions.
The results obtained can be applied to determine minimax estimators of a cumulative distribution function and minimax estimators
of a survival function. 相似文献
102.
Protfolio optimization is very sensitive to the forecats of returns and (co-)variances of the underlying assets. This paper
applies a Bayesian vector-autoregression of the asset universe to predict the returns. Further, the co-variance matrix is
forecasted by an Augmented GARCH estimation of the most volatile principle components of the return series. As an empirical
illustration, the daily stock returns of the German stocks index DAX have been used to calculate some well-known mean-variance
portfolios. Back-testing is used to evaluate the performance. The approach seems to be promising. 相似文献
103.
This paper developed an exact method of random permutations when testing both interaction and main effects in the two-way
ANOVA model. The method of this paper can be regarded as a much improved model when compared with those of the previous studies
such as Still and White (1981) and ter Braak (1992). We further conducted a simulation experiment in order to check the statistical
performance of the proposed method. The proposed method works relatively well for small sample sizes compare with the existing
methods.
This work was supported by Korea Science and Engineering Foundation Grant (R14-2003-002-0100) 相似文献
104.
Gabriela Beganu 《Statistical Methods and Applications》2007,16(3):347-356
It is known that the Henderson Method III (Biometrics 9:226–252, 1953) is of special interest for the mixed linear models
because the estimators of the variance components are unaffected by the parameters of the fixed factor (or factors). This
article deals with generalizations and minor extensions of the results obtained for the univariate linear models. A MANOVA
mixed model is presented in a convenient form and the covariance components estimators are given on finite dimensional linear
spaces. The results use both the usual parametric representations and the coordinate-free approach of Kruskal (Ann Math Statist
39:70–75, 1968) and Eaton (Ann Math Statist 41:528–538, 1970). The normal equations are generalized and it is given a necessary
and sufficient condition for the existence of quadratic unbiased estimators for covariance components in the considered model. 相似文献
105.
106.
Breslow and Holubkov (J Roy Stat Soc B 59:447–461 1997a) developed semiparametric maximum likelihood estimation for two-phase
studies with a case–control first phase under a logistic regression model and noted that, apart for the overall intercept
term, it was the same as the semiparametric estimator for two-phase studies with a prospective first phase developed in Scott
and Wild (Biometrica 84:57–71 1997). In this paper we extend the Breslow–Holubkov result to general binary regression models
and show that it has a very simple relationship with its prospective first-phase counterpart. We also explore why the design
of the first phase only affects the intercept of a logistic model, simplify the calculation of standard errors, establish
the semiparametric efficiency of the Breslow–Holubkov estimator and derive its asymptotic distribution in the general case. 相似文献
107.
The main goal of the paper is to specify a suitable multivariate multilevel model for polytomous responses with a non-ignorable
missing data mechanism in order to determine the factors which influence the way of acquisition of the skills of the graduates
and to evaluate the degree programmes on the basis of the adequacy of the skills they give to their graduates. The application
is based on data gathered by a telephone survey conducted, about two years after the degree, on the graduates of year 2000
of the University of Florence. A multilevel multinomial logit model for the response of interest is fitted simultaneously
with a multilevel logit model for the selection mechanism by means of maximum likelihood with adaptive Gaussian quadrature.
In the application the multilevel structure has a crucial role, while selection bias results negligible. The analysis of the
empirical Bayes residuals allows to detect some extreme degree programmes to be further inspected. 相似文献
108.
Let X
1, X
2,... be iid random variables (rv's) with the support on nonnegative integers and let (W
n
, n≥0) denote the corresponding sequence of weak record values. We obtain new characterization of geometric and some other discrete
distributions based on different forms of partial independence of rv's W
n
and W
n+r
—W
n
for some fixed n≥0 and r≥1. We also prove that rv's W
0 and W
n+1
—W
n
have identical distribution if and only if (iff) the underlying distribution is geometric. 相似文献
109.
Thomas DC 《Lifetime data analysis》2007,13(4):565-581
I consider the design of multistage sampling schemes for epidemiologic studies involving latent variable models, with surrogate
measurements of the latent variables on a subset of subjects. Such models arise in various situations: when detailed exposure
measurements are combined with variables that can be used to assign exposures to unmeasured subjects; when biomarkers are
obtained to assess an unobserved pathophysiologic process; or when additional information is to be obtained on confounding
or modifying variables. In such situations, it may be possible to stratify the subsample on data available for all subjects
in the main study, such as outcomes, exposure predictors, or geographic locations. Three circumstances where analytic calculations
of the optimal design are possible are considered: (i) when all variables are binary; (ii) when all are normally distributed;
and (iii) when the latent variable and its measurement are normally distributed, but the outcome is binary. In each of these
cases, it is often possible to considerably improve the cost efficiency of the design by appropriate selection of the sampling
fractions. More complex situations arise when the data are spatially distributed: the spatial correlation can be exploited
to improve exposure assignment for unmeasured locations using available measurements on neighboring locations; some approaches
for informative selection of the measurement sample using location and/or exposure predictor data are considered. 相似文献
110.
In this paper, reversed preservation properties of right spread order, total time on test order and increasing convex (concave)
order when taking random minima and maxima are developed. In this context, reversed preservation properties of some ageing
concepts are investigated under parallel (series) systems which are composed of a random number of i.i.d. components. Some applications in reliability and economics are given. 相似文献