Some results on optimality in models with heteroscedastic errors from partial optimum designs

This paper studies optimum designs for linear models when the errors are heteroscedastic. Sufficient conditions are given in order to obtainD-, A- andE-optimum designs for a complete regression model from partial optimum designs for some sub-parameters. A result about optimality for a complete model from the optimality for the submodels is included. Supported by Junta de Andalucía, research group FQM244.     

Simple detection of outlying short time series

Sets of relatively short time series arise in many situations. One aspect of their analysis may be the detection of outlying series. We examine the performance of standard normal outlier tests applied to the means, or to simple functions of the means, of AR(1) series, not necessarily of equal lengths. Although unequal lengths of series implies that the means have unequal variances, that are only known approximately, it is shown that nominal significance levels hold good under most circumstances. Thus a standard outlier test can usefully be applied, avoiding the complication of estimating the time series' parameters. The test's power is affected by unequal lengths, being higher when the slippage occurs in one of the longer series     

Tools for decision making under imprecise risk

Generalizing risk, imprecise risk is a situation where available objective information is expressible by a lower probability. We study properties of certain lower probabilities in metrizable spaces. Necessary and sufficient conditions are derived for stability of their cores under image and mixture, which are useful features in applying Expected Utility Theory under imprecise risk. Received: December 2000; revised version: March 2001     

Non parametric mixture priors based on an exponential random scheme

We propose a general procedure for constructing nonparametric priors for Bayesian inference. Under very general assumptions, the proposed prior selects absolutely continuous distribution functions, hence it can be useful with continuous data. We use the notion ofFeller-type approximation, with a random scheme based on the natural exponential family, in order to construct a large class of distribution functions. We show how one can assign a probability to such a class and discuss the main properties of the proposed prior, namedFeller prior. Feller priors are related to mixture models with unknown number of components or, more generally, to mixtures with unknown weight distribution. Two illustrations relative to the estimation of a density and of a mixing distribution are carried out with respect to well known data-set in order to evaluate the performance of our procedure. Computations are performed using a modified version of an MCMC algorithm which is briefly described.     

Quasi-likelihood from<Emphasis Type="Italic">M</Emphasis>-estimators: A numerical comparison with empirical likelihood

In this paper we compare two robust pseudo-likelihoods for a parameter of interest, also in the presence of nuisance parameters. These functions are obtained by computing quasi-likelihood and empirical likelihood from the estimating equations which define robustM-estimators. Application examples in the context of linear transformation models are considered. Monte Carlo studies are performed in order to assess the finite-sample performance of the inferential procedures based on quasi-and empirical likelihood, when the objective is the construction of robust confidence regions.     

Choice and circumstance: Qualitative insights into contemporary childlessness in Australia

Using data from in-depth interviews with 115 women, men and couples in eastern Australia for whom family formation was a recent, current or imminent future issue, this article explores contemporary childlessness among those physically able to have children. It differentiates between those childless by choice and by circumstance, and among other themes highlights (i) the role preservation of lifestyle appears to play as a motive for deliberate childlessness following development of a life course through early adulthood that both generates lifestyle aspirations and often places parenthood on the backburner until after age 30, and (ii) the roles difficulty forming suitable relationships, women’s desire for meaningful careers, and male involvement in family formation decisions play in bringing about childlessness by circumstance.     

Recent Life Expectancy Divergence in Baltic Countries

Until the end of the 1990s, mortality patterns and trends in Estonia, Latvia and Lithuania were remarkably similar. However, from the year 2000 onwards, life expectancy trends in the three countries started to diverge. In particular, sustainable progress in Estonia over the period 2000–2007 contrasts with stagnation in Latvia, and even worsening trends in Lithuania. These contradictory changes seem to be mainly explained by contrasting dynamics in mortality from cardiovascular diseases, external causes of death and digestive system diseases. Whereas cardiovascular and external-cause mortality declined in Estonia and Latvia, worsening or stagnation of mortality from these causes of death was observed in Lithuania. The negative mortality changes in Lithuania were also reinforced by a striking increase in mortality from alcohol-related digestive system diseases. The findings suggest that the divergence in health trends between the three countries may be attributable to their varying degrees of success in implementing structural health care reforms and specific health policy measures. By contrast, the very recent improvement (since 2008) is parallel in the three countries and is largely because of the introduction of rather similar anti-alcohol measures.