Likelihood analysis for a class of beta mixed models

Beta regression is a suitable choice for modelling continuous response variables taking values on the unit interval. Data structures such as hierarchical, repeated measures and longitudinal typically induce extra variability and/or dependence and can be accounted for by the inclusion of random effects. In this sense, Statistical inference typically requires numerical methods, possibly combined with sampling algorithms. A class of Beta mixed models is adopted for the analysis of two real problems with grouped data structures. We focus on likelihood inference and describe the implemented algorithms. The first is a study on the life quality index of industry workers with data collected according to an hierarchical sampling scheme. The second is a study assessing the impact of hydroelectric power plants upon measures of water quality indexes up, downstream and at the reservoirs of the dammed rivers, with a nested and longitudinal data structure. Results from different algorithms are reported for comparison including from data-cloning, an alternative to numerical approximations which also allows assessing identifiability. Confidence intervals based on profiled likelihoods are compared with those obtained by asymptotic quadratic approximations, showing relevant differences for parameters related to the random effects. In both cases, the scientific hypothesis of interest was investigated by comparing alternative models, leading to relevant interpretations of the results within each context.     

Aging in the Third World

The relationships between the generations in Third World countries are changing as migration and industrialization erode traditional family responsibilities for supporting the elderly. It is no longer possible to assume that, as a matter of course, old people will be looked after by their families. Social change leads to an eroding of the support systems. The author finds growing evidence of this breakdown in Asia, particularly in Singapore, Hong Kong, and other highly industrialized centers. Singapore, for example, has reinstituted the compulsory study of filial piety in an attempt to push the younger generation into assuming its traditional responsibility toward the old. There has also been a significant decline in the status, prestige, and support given old people in Indonesia, although politicans insist that the family will always take care of its elderly. 2 reasons for this breakdown are 1) the impact of the mass media and 2) the increasing involvement of the younger generation in non-agricultural jobs which often involve a move to the city and away from dependence on a patriarch. Many Third World countries are in a twilight stage, between the traditionally strong structure of family support and government systems of social security.     

Cedar Point: A Park in Progress

This is a biography of an amusement park, Cedar Point in Sandusky, Ohio, by its marketing director. This life history, using sources close to the park and in the popular press ouer many decades, traces the many shifts in circumstance, philosophy and mood in its development ouer a span from 1897 to its present status as “one of the great parks of the country.” This case study of a single park that has incorporated characteristics of many growth stages ofparks ingeneral serues as a capsule history: from its beginnings as a resort; expansion of rides and attractions during the flush years of the 1920s; the backsliding deterioration of the Depression years and the immediatepost- War period; the decline of the big-city parks and the moue to the suburbs in the 50s; and the Disney effect: the advent of the national super theme park, with its revolutionary impact on the traditional park concept. According to Hildebrandt, Cedar Point is “the only modern superpark that also has an ancient history…. the only old-time amusement park to successfully make the transition to the new amusement park culture.”     

Migration and climate change: examining thresholds of change to guide effective adaptation decision-making

The implications of environmental change for migration are little understood. Migration as a response to climate change could be seen as a failure of in situ adaptation methods, or migration could be alternatively perceived as a rational component of creative adaptation to environmental risk. This paper frames migration as part of an adaptation response to climate change impacts to natural resource condition and environmental hazards. Thresholds will be reached by communities after which migration will become a vital component of an effective adaptation response. Such changes to migration patterns have the potential to undermine migration policy unless appropriate preparations are undertaken. This paper describes an approach to assist researchers to frame how climate change will influence migration by critically analysing how thresholds of fundamental change to migration patterns could be identified, primarily in relation to two case studies in Nepal and Thailand. Future policy for internal and international migration could be guided by the analysis of such thresholds of non-linear migration and resourced effectively to ensure that socio-economic and humanitarian outcomes are maximised.     

Temporary Skilled Migration to Australia: Employers' Perspectives1

With the 1996 introduction of a new visa making it easier for employers to sponsor skilled foreign workers, temporary skilled migration has become a significant component of international migration flows to Australia. This paper examines employers' reasons for sponsoring skilled workers from abroad, their modes of recruitment, the occupational skills they require, and their industry profile. We also discuss issues relating to the perception of a shortage of skilled workers, the extent that sponsoring foreign workers substitutes for investing in local training, and the role of networks in recruiting overseas workers. Many employers' now have a global view of labour recruitment. While this is understandable for multinational companies with global operations, many small businesses and public sector institutions are adopting the same strategy to obtain skilled labour which they say is in short supply in Australia. With the internationalization of the Australian economy, there is also an increasing demand for people with specialized skills and knowledge that is not available in Australia's relatively small labour market. An understanding of the demand factors motivating temporary skilled migration is crucial to effectively managing Australia's migration and labour trends.     

On multiple constraint skewed models

The Azzalini [A. Azzalini, A class of distributions which includes the normal ones, Scandi. J. Statist. 12 (1985), pp. 171–178.] skew normal model can be viewed as one involving normal components subject to a single linear constraint. As a natural extension of this model, we discuss skewed models involving multiple linear and nonlinear constraints and possibly non-normal components. Particular attention is devoted to a distribution called the extended two-piece normal (ETN) distribution. This model is a two-constraint extension of the two-piece normal model introduced by Kim [H.J. Kim, On a class of two-piece skew normal distributions, Statistics 39(6) (2005), pp. 537–553.]. Likelihood inference for the ETN distribution is developed and illustrated using two data sets.     

The 'Scottish' Approach? The discursive construction of a national police force

In 2005, the location of the G8 summit meeting in Gleneagles, Scotland, brought the contested boundaries of the state and the nation to the fore. Confronted by the prospect of significant public disorder police forces in Scotland routinely flagged up a 'Scottish approach to policing'. Drawing on research with key police officers and others we explore the processes through which national identities come to be articulated, contested and acted out in the context of one particular institution: the police. We consider the claim that policing of the summit was 'Scottish' and assess the implications of this assertion. Whilst the police have been argued to be integral to the constitution and expression of nation-statehood we highlight the dangers in an uncritical acceptance of police philosophies and also point to the banal ways in which national identity is naturalised.     

Bimodality based on the generalized skew-normal distribution

This paper focuses on the development of a new extension of the generalized skew-normal distribution introduced in Gómez et al. [Generalized skew-normal models: properties and inference. Statistics. 2006;40(6):495–505]. To produce the generalization a new parameter is introduced, the signal of which has the flexibility of yielding unimodal as well as bimodal distributions. We study its properties, derive a stochastic representation and state some expressions that facilitate moments derivation. Maximum likelihood is implemented via the EM algorithm which is based on the stochastic representation derived. We show that the Fisher information matrix is singular and discuss ways of getting round this problem. An illustration using real data reveals that the model can capture well special data features such as bimodality and asymmetry.     

Bayesian analysis of skew-normal independent linear mixed models with heterogeneity in the random-effects population

We present a new class of models to fit longitudinal data, obtained with a suitable modification of the classical linear mixed-effects model. For each sample unit, the joint distribution of the random effect and the random error is a finite mixture of scale mixtures of multivariate skew-normal distributions. This extension allows us to model the data in a more flexible way, taking into account skewness, multimodality and discrepant observations at the same time. The scale mixtures of skew-normal form an attractive class of asymmetric heavy-tailed distributions that includes the skew-normal, skew-Student-t, skew-slash and the skew-contaminated normal distributions as special cases, being a flexible alternative to the use of the corresponding symmetric distributions in this type of models. A simple efficient MCMC Gibbs-type algorithm for posterior Bayesian inference is employed. In order to illustrate the usefulness of the proposed methodology, two artificial and two real data sets are analyzed.     

The parents' share

A 5 item sexual permissiveness scale devised by Reiss, and 4 personality inventory scales purporting to measure psychoticism (P), neuroticism (N), extraversion (E) and propensity to dissimulate (L for lie scale) were administered to 427 male and 436 female subjects aged between 20 and 50 years. It was found that men were more permissive than women on all 5 items; that items are intercorrelated in a pattern which could be predicted from the Guttman‐type properties of the original scale; that high P scorers were more permissive than low P scorers; that high L scorers were less permissive than low L scorers; and that extraverts were slightly more permissive than introverts. All the findings relating to personality and permissiveness were in good agreement with findings from previous studies of the relation between personality and sexual attitudes. Assortative mating was studied for 241 couples who formed part of the original sample. Correlations for permissiveness were all positive, and reached significance for all but one of the scales. For the personality scales, assortative mating was found to be important only for neuroticism, a finding in agreement with previous studies.