HEAVY-TAILED-DISTRIBUTED THRESHOLD STOCHASTIC VOLATILITY MODELS IN FINANCIAL TIME SERIES

To capture mean and variance asymmetries and time‐varying volatility in financial time series, we generalize the threshold stochastic volatility (THSV) model and incorporate a heavy‐tailed error distribution. Unlike existing stochastic volatility models, this model simultaneously accounts for uncertainty in the unobserved threshold value and in the time‐delay parameter. Self‐exciting and exogenous threshold variables are considered to investigate the impact of a number of market news variables on volatility changes. Adopting a Bayesian approach, we use Markov chain Monte Carlo methods to estimate all unknown parameters and latent variables. A simulation experiment demonstrates good estimation performance for reasonable sample sizes. In a study of two international financial market indices, we consider two variants of the generalized THSV model, with US market news as the threshold variable. Finally, we compare models using Bayesian forecasting in a value‐at‐risk (VaR) study. The results show that our proposed model can generate more accurate VaR forecasts than can standard models.     

Estimating the distribution function using k-tuple ranked set samples

The basic assumption underlying the concept of ranked set sampling is that actual measurement of units is expensive, whereas ranking is cheap. This may not be true in reality in certain cases where ranking may be moderately expensive. In such situations, based on total cost considerations, k-tuple ranked set sampling is known to be a viable alternative, where one selects k units (instead of one) from each ranked set. In this article, we consider estimation of the distribution function based on k-tuple ranked set samples when the cost of selecting and ranking units is not ignorable. We investigate estimation both in the balanced and unbalanced data case. Properties of the estimation procedure in the presence of ranking error are also investigated. Results of simulation studies as well as an application to a real data set are presented to illustrate some of the theoretical findings.     

Examples of the use of an equivalence theorem in constructing optimum experimental designs for random-effects nonlinear regression models

The problem considered is that of finding an optimum measurement schedule to estimate population parameters in a nonlinear model when the patient effects are random. The paper presents examples of the use of sensitivity functions, derived from the General Equivalence Theorem for D-optimality, in the construction of optimum population designs for such schedules. With independent observations, the theorem applies to the potential inclusion of a single observation. However, in population designs the observations are correlated and the theorem applies to the inclusion of an additional measurement schedule. In one example, three groups of patients of differing size are subject to distinct schedules. Numerical, as opposed to analytical, calculation of the sensitivity function is advocated. The required covariances of the observations are found by simulation.     

Multivariate distributions defined in terms of contours

The paper deals with the problem of using contours as the basis for defining probability distributions. First, the most general probability densities with given contours are obtained and the particular cases of circular and elliptical contours are dealt with. It is shown that the so-called elliptically contoured distributions do not include all possible cases. Next, the case of contours defined by polar coordinates is analyzed including its simulation and parameter estimation. Finally, the case of cumulative distribution functions with given contours is discussed. Several examples are used for illustrative purposes.     

Asymptotic posterior normality for multiparameter problems

For asymptotic posterior normality in the one-parameter cases, Weng [2003. On Stein's identity for posterior normality. Statist. Sinica 13, 495–506] proposed to use a version of Stein's Identity to write the posterior expectations for functions of a normalized quantity in a form that is more transparent and can be easily analyzed. In the present paper we extend this approach to the multi-parameter cases and compare our conditions with earlier work. Three examples are used to illustrate the application of this method.     

论高海拔地区人类生殖能力的研究:回应霍夫

霍夫的评论表明,那些叙述高海拔缺氧影响人类生育力和生殖能力的文献中弥漫着方法论和概念的迷雾.我们去年的文章主题也谈到了这一点(见<美国人类学家>85:28-49,1983).我们的论文尽力阐述了喜马拉雅山脉的高海拔地区,藏语族群中普遍存在的不同生育力水平,是与某些文献的报道一致的.     

Children of Adolescent Mothers: Cognitive and Behavioral Status at Age Six

The cognitive and behavioral status at age six years of 185 children of adolescent mothers (60.5% boys) were assessed using the mother (CBCL) and teacher (TRF) report forms of the Child Behavior Checklist and the Bracken Basic Concepts Scale. There was evidence for impairment in all areas of functioning. More than half of the sample exceeded the borderline clinical cutoff (T = 60) on either the CBCL or TRF Total Problem score, and nearly half the sample had Bracken scores that were more than 1 SD below the normative mean. Only 26.9% of the children were in the normal range on all three measures. These results are discussed in terms of implications for social work practice with children and adolescent mother families.     

Gender Competition and the Preservation of Community in the Allocation of Administrative Positions in Small Rural Towns in Montana: A Research Note1

Abstract Assignment of administrative positions in a sample of rural towns is demonstrated to be significantly associated with gender. Most civil administrators are women, while most legal and educational administrators are men. The difference indicates structural assignment of positions by gender. Gender and administrative position are demonstrated to have zero-order correlations with perceptions of two important behaviors for community: migration and social problems. The characteristics of the occupation and of the administrators are qualitatively different. The data are compiled from interviews with seventy administrators in five pairs of small towns in Montana, ranging in size from about 200 to approximately 7,000 residents. Each pair contains one agricultural and one scenic recreational town. Comparatively, more women were employed in agricultural towns. Many rural women who become administrators, particularly long-term administrators, may be selected for reasons that help preserve the community by providing opportunities for themselves and their families.     

Interparental Conflict and Preschoolers' Peer Relations: The Moderating Roles of Temperament and Gender

The relations between destructive interparental conflict (IPC) and three‐ to six‐year‐olds’ (N = 62) peer relations were examined as a function of child temperament and gender. Regression analyses indicated that effortful control moderated the relations of IPC with children's amount of peer interaction as well as with their problematic relations with peers. Specifically, high IPC was associated with low amount of interaction and high problematic relations for preschoolers low in effortful control, but it was related to high amount of interaction and low problems for those high in effortful control. Additionally, gender differences in the relations between IPC and the amount of peer interaction indicated that IPC was negatively related to the amount of interaction for girls but positively related to the amount for boys. The findings highlight the need for examining individual differences in the relations between IPC and the development of early peer relations.     

The Continued Importance of Quality Parent–Adolescent Relationships During Late Adolescence

The quality of adolescents' relationships with residential parents has been found to predict many different health and behavioral youth outcomes; strong associations have also been found between these outcomes and family processes, and between relationship quality and family processes. Data from Rounds 1–5 of the National Longitudinal Survey of Youth, 1997 were used to examine hypotheses about the influence of the parent–adolescent relationship on subsequent adolescent mental well‐being and delinquency, as mediated by family processes. Using structural equation modeling, we found that the influence of a positive residential parent–adolescent relationship on better mental well‐being and fewer delinquency was entirely mediated by family routines, parental monitoring, and parental supportiveness, net of sociodemographic controls.