The growth curve model: a review

A survey is given of papers which have influenced or have been influenced by the Growth Curve Model due to Potthoff & Roy (1964). The review covers, among others, methods of estimating parameters, the canonical version of the model, tests, extensions, incomplete data, Bayesian approaches and covariance structures.     

Longitudinal models for polytomous responses

Recent work by Miller and Landis (1991) discusses generalized variance component models for polytomous responses. This work is adapted to longitudinal models for repeated measures of individuals having polytomous responses. In this setting, individuals are considered to be “clusters”. The resulting simplifications are discussed. First, each response has a multinomial distribution with N=l. Second, observed cluster proportions in the variance component estimates must be replaced by their expectations. This technique accommodates patients with missing data in a sequence of repeated observations.     

Wilson Confidence Intervals for the Two-Sample Log-Odds-Ratio in Stratified 2 × 2 Contingency Tables

Large-sample Wilson-type confidence intervals (CIs) are derived for a parameter of interest in many clinical trials situations: the log-odds-ratio, in a two-sample experiment comparing binomial success proportions, say between cases and controls. The methods cover several scenarios: (i) results embedded in a single 2 × 2 contingency table; (ii) a series of K 2 × 2 tables with common parameter; or (iii) K tables, where the parameter may change across tables under the influence of a covariate. The calculations of the Wilson CI require only simple numerical assistance, and for example are easily carried out using Excel. The main competitor, the exact CI, has two disadvantages: It requires burdensome search algorithms for the multi-table case and results in strong over-coverage associated with long confidence intervals. All the application cases are illustrated through a well-known example. A simulation study then investigates how the Wilson CI performs among several competing methods. The Wilson interval is shortest, except for very large odds ratios, while maintaining coverage similar to Wald-type intervals. An alternative to the Wald CI is the Agresti-Coull CI, calculated from the Wilson and Wald CIs, which has same length as the Wald CI but improved coverage.     

A Description of Disordered Eating Behaviors in Latino Males

Abstract

Objective: To explore disordered eating and eating disorders (EDs) in Latino males. Participants: Participants are 722 male college students from a larger prevalence study conducted in the University of Puerto Rico system. Methods: Participants were selected from a list of sections of required courses for first-year students on each campus. Self-report instruments were used to explore ED symptoms (the Eating Attitudes Test [EAT-26] and the Bulimia Test–Revised [BULIT-26-R] and the Beck Depression Inventory depression (BDI). Results: Overall, 2.26% scored above the cut-off point on the BULIT-R and 5.08% score above the cut-off point on the EAT-26. Of the males, 4.43% reported sufficient frequency and severity to approximate DSM-IV criteria for bulimia nervosa. Depression symptomatology was found in those who scored above the cut-off point on both instruments of EDs. Conclusion: College health practitioners should be aware of disordered eating in Latino males and include them in efforts to detect disordered eating behaviors in college students.     

Rebound effects of progress in information technology

Information technology (IT) is continuously making astounding progress in technical efficiency. The time, space, material and energy needed to provide a unit of IT service have decreased by three orders of magnitude since the first personal computer (PC) was sold. However, it seems difficult for society to translate IT’s efficiency progress into progress in terms of individual, organizational or socio-economic goals. In particular it seems to be difficult for individuals to work more efficiently, for organizations to be more productive and for the socio-economic system to be more sustainable by using increasingly efficient IT. This article provides empirical evidence and potential explanations for this problem. Many counterproductive effects of IT can be explained economically by rebound effects. Beyond that, we conclude that the technological determinism adopted by decision-makers is the main obstacle in translating IT’s progress into non-technical goals.

Combined work stresses: Effect of reduced air renewal on psychological performance during 72h sustained operations

Human tolerance limits for sustained operations under the combined stress of stale air and sleep loss were studied in two groups often male volunteers over a 72 h period, with only 1h of sleep permitted after 32, 48 and 60h. The experiment investigated whether such sustained performance might be additionally influenced by mild hypoxia (15 vol% O₂) together with correspondingly increased carbon dioxide levels (5 vol%).

Performance on various psychological tests showed the expected decrease with increasing duration of sleep loss. However, there were no clear cut differences in performance between the control and the hypoxia groups. There were, however, more pronounced decreases with time in either group in the more complex tasks as compared to simple reaction time and vigilance tasks. Short-term memory improved probably due to learning. The missing effect of hypoxia could be attributed to a hyperventilation response in the experimental subjects and an increase in cerebral blood flow initiated by the hypercapnia.     

A Joint Stakeholder Learning Process in Participatory Environmental Ethics: A Case Study

There is a growing need to study the dynamic interdependence between business and society as a reciprocal relationship which ought to be supported and not constrained by refocusing on ethical values. Instead of describing how economic institutions impact society, the new view attempts to analyze how stakeholders‘ views and concerns affect business corporations‘ strategy assessment and formation processes. These processes can be enhanced by a renewed awareness of the moral issues at stake. The case describes the Norwegian aluminium industry‘s collective effort to gain not only deeper scientific insight into their impact on the environment but also increase their understanding of their stakeholders‘ concerns. As the analysis shows the process was definitely strengthened through what the author calls the principle of participative dialogue with stakeholders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Population pressures in Latin America

In 1950 Latin America's population of 165 million was on a par with the 166 million of North America. 2 decades of growth at nearly 3% a year pushed the total to 405 million in 1985, vs. 264 million in North America. Despite substantial fertility declines since the 1960s, continued growth is ensured by the demographic momentum built into the region's large and youthful population bases. UN medium projections put the 2025 total at 779 million, compared to 345 million in North America. This Bulletin examines the main demographic changes in Latin America since World War II and their links to economic and social changes in the region as well as their implications for international and social relations. The post World War II population surge was accompanied by massive rural-ruban and international migration, rapid urbanization, large labor shifts out of agriculture into industry and services, increased education for both men and women, and higher labor force participation for females. The rural exodus was spurred by extreme land tenure inequalities and the urban bias of postwar industrialization. The labor-saving bias of this industrialization forced exploding city populations to turn to the informal sector for jobs. Population pressures on city services and housing as well as jobs have been further exacerbated by overconcentration in a few large cities and economic downturns of the 1980s. Recent fertility declines seem to be the result of both increased access to family planning and the economic and social pressures posed by the gap between young adults' aspirations and their ability to realize them. Population and economic pressures could induce faster fertility declines than now projected but in the short run are likely to mean more employment problems, continued rapid urban growth, and even larger international immigration flows within the hemisphere, particularly to the US.