Bayesian inference and model comparison for asymmetric smooth transition heteroskedastic models

Inference, quantile forecasting and model comparison for an asymmetric double smooth transition heteroskedastic model is investigated. A Bayesian framework in employed and an adaptive Markov chain Monte Carlo scheme is designed. A mixture prior is proposed that alleviates the usual identifiability problem as the speed of transition parameter tends to zero, and an informative prior for this parameter is suggested, that allows for reliable inference and a proper posterior, despite the non-integrability of the likelihood function. A formal Bayesian posterior model comparison procedure is employed to compare the proposed model with its two limiting cases: the double threshold GARCH and symmetric ARX GARCH models. The proposed methods are illustrated using both simulated and international stock market return series. Some illustrations of the advantages of an adaptive sampling scheme for these models are also provided. Finally, Bayesian forecasting methods are employed in a Value-at-Risk study of the international return series. The results generally favour the proposed smooth transition model and highlight explosive and smooth nonlinear behaviour in financial markets.     

A case-based distance method for screening in multiple-criteria decision aid

Screening is a process of multiple-criteria decision aid (MCDA) in which a large set of alternatives is reduced to a smaller set that most likely contains the best choice. We propose screening using a distance model calibrated on the basis of the decision-maker's own judgement. Viewing MCDA as preference aggregation based on consequence data, we define consequence and preference expressions (values and weights) and describe how they are aggregated. Then we define screening and explain some of its properties. Using an appropriate definition of distance, our case-based distance method screens a set of alternatives using criterion weights and a distance threshold obtained by quadratic optimization using the decision-maker's selection of alternatives from a test set. This case-based method can elicit the decision maker's preferences more expeditiously and accurately than direct inquiry. An application in water supply planning is used to demonstrate the procedure.     

The muse as mother

This paper suggests that the concept of the muse in relation to the creative process is more than a myth or cultural artifact. It is argued that the muse is a psychic recollection of our memories of the female who presided over our first experiences of consciousness as we traversed the borders of inner and outer reality—that is, the mother. The shift of consciousness required in creative activity triggers recall of this figure. Object relations theory, recent findings from infant research, and the intuitive observations of several authors are used to support this thesis. Clinical examples illustrate the application of this concept in treatment.     

OCCUPATIONAL SEX SEGREGATION AND ECONOMIC INEQUALITY UNDER SOCIALISM:

An increase in scholarly attention to income differences between sex-typed occupations has generated a burgeoning literature. Typically-female occupations require preemployment education, not prolonged on-the-job training; receive less renumeration for work autonomy than male-typed occupations; and are concentrated in economically disadvantaged industrial sectors. However, these issues have received only preliminary consideration regarding noncapitalist societies and research has lacked an integrative, analytical focus. This study compares the earnings effects of education, type of work, and industrial sector between female- and male-dominated occupations in socialist Yugoslavia. As expected, average earnings are significantly higher in male than in female occupations. The results from the earnings regressions reveal a higher explained variance and larger economic returns to education among female- dominated occupations, especially in the managerial and professional strata. A decomposition of the earnings difference between sex-typed occupations suggests a variation in the source of inequality across skill strata. In the discussion, a comparison of capitalism and socialism reveals that while some aspects of the earnings attainment process may be unique to socialism, others are not.     

Random regression models for human immunodeficiency virus ribonucleic acid data subject to left censoring and informative drop-outs

Objectives in many longitudinal studies of individuals infected with the human immunodeficiency virus (HIV) include the estimation of population average trajectories of HIV ribonucleic acid (RNA) over time and tests for differences in trajectory across subgroups. Special features that are often inherent in the underlying data include a tendency for some HIV RNA levels to be below an assay detection limit, and for individuals with high initial levels or high ranges of change to drop out of the study early because of illness or death. We develop a likelihood for the observed data that incorporates both of these features. Informative drop-outs are handled by means of an approach previously published by Schluchter. Using data from the HIV Epidemiology Research Study, we implement a maximum likelihood procedure to estimate initial HIV RNA levels and slopes within a population, compare these parameters across subgroups of HIV-infected women and illustrate the importance of appropriate treatment of left censoring and informative drop-outs. We also assess model assumptions and consider the prediction of random intercepts and slopes in this setting. The results suggest that marked bias in estimates of fixed effects, variance components and standard errors in the analysis of HIV RNA data might be avoided by the use of methods like those illustrated.     

PROBLEMS WITH BINOMIAL TWO-SIDED TESTS AND THE ASSOCIATED CONFIDENCE INTERVALS

Confidence intervals for parameters of distributions with discrete sample spaces will be less conservative (i.e. have smaller coverage probabilities that are closer to the nominal level) when defined by inverting a test that does not require equal probability in each tail. However, the P‐value obtained from such tests can exhibit undesirable properties, which in turn result in undesirable properties in the associated confidence intervals. We illustrate these difficulties using P‐values for binomial proportions and the difference between binomial proportions.