Flexible estimates of tumour incidence for intermediately lethal tumours in a typical long-term animal bioassay

The estimation of the incidence of tumours in an animal carcinogenicity study is complicated by the occult nature of the tumours involved (i.e. tumours are not observable before an animal's death). Also, the lethality of tumours is generally unknown, making the tumour incidence function non-identifiable without interim sacrifices, cause-of-death data or modelling assumptions. Although Kaplan–Meier curves for overall survival are typically displayed, obtaining analogous plots for tumour incidence generally requires fairly elaborate model fitting. We present a case-study of tetrafluoroethylene to illustrate a simple method for estimating the incidence of tumours as a function of more easily estimable components. One of the components, tumour prevalence, is modelled by using a generalized additive model, which leads to estimates that are more flexible than those derived under the usual parametric models. A multiplicative assumption for tumour lethality allows for the incorporation of concomitant information, such as the size of tumours. Our approach requires only terminal sacrifice data although additional sacrifice data are easily accommodated. Simulations are used to illustrate the estimator proposed and to evaluate its properties. The method also yields a simple summary measure of tumour lethality, which can be helpful in interpreting the results of a study.     

Changes in world inequality in length of life: 1970–2000

Previous research has revealed much global convergence over the past several decades in life expectancy at birth and in infant mortality, which are closely linked. But trends in the variance of length of life, and in the variance of length of adult life in particular, are less well understood. I examine life-span inequality in a comprehensive panel of 180 countries observed in 1970 and 2000. Convergence in infant mortality has unambiguously reduced world inequality in total length of life starting from birth, but world inequality in length of adult life has remained largely unchanged. Underlying both of these observations is a growing share of total inequality attributable to between-country variation. Especially among developed countries, the absolute level of between-country inequality has risen over time. The sources of widening inequality in length of life between countries remain unclear, but signs point away from changes in income, leaving patterns of knowledge diffusion as a likely candidate.     

Expatriate labour markets in rapidly globalising cities: reproducing the migrant division of labour in Abu Dhabi and Dubai

This paper studies the processes through which skilled international workers are differentially attracted to and incorporated in the rapidly globalising cities of Dubai and Abu Dhabi, thereby reproducing the migrant division of labour in these cities. This is accomplished by presenting results from a large-scale employment survey of foreign and local firms in these cities, as well as key informant interviews conducted with representatives of these firms. Most significantly, it is in global city labour markets that firm employment practices intersect with state regulatory frameworks and local employment structures, and thus, where skilled international migration flows are localised.     

Number of predictors and multicollinearity: What are their effects on error and bias in regression?

The present Monte Carlo simulation study adds to the literature by analyzing parameter bias, rates of Type I and Type II error, and variance inflation factor (VIF) values produced under various multicollinearity conditions by multiple regressions with two, four, and six predictors. Findings indicate multicollinearity is unrelated to Type I error, but increases Type II error. Investigation of bias suggests that multicollinearity increases the variability in parameter bias, while leading to overall underestimation of parameters. Collinearity also increases VIF. In the case of all diagnostics however, increasing the number of predictors interacts with multicollinearity to compound observed problems.     

Some issues in logistic regression

Much research has been performed in the area of multiple linear regression, with the resuit that the field is well-developed. This is not true of logistic regression, however. The latter presents special problems because the response is not continuous. Some of these problems are: the difficulty of developing a suitable R² statistic, possibly poor results produced by the method of maximum likelihood, and the challenge to develop suitable graphical techniques. We describe recent work in some of these directions, and discuss the need for additional research.     

Most and Least Meaningful Learning Experiences in Marriage and Family Therapy Education

Marriage and family therapy educators increasingly emphasize training competencies. What we know less about is what makes family therapy education meaningful to marriage and family therapy (MFT) graduate students and what does not. In this study, through an Internet survey, we explored the most and least meaningful learning experiences of 68 MFT graduate students and recent graduates of Commission on Accreditation for Marriage and Family Therapy Education—accredited programs. We used thematic analysis to identify and illustrate resulting themes, which included the importance of experiential and personal components to learning, the professor‐student alliance, tying theory to practice, and the experiences of students with their clients, among others. We discuss the implications of these findings to support family therapy education and offer tentative suggestions for formative discussions both within and across programs. Video Abstract is found in the online version of the article .     

Disengaged or Bookworm: Academics,Mental Health,and Success for Sexual Minority Youth

Same‐sex attracted youth (SSAY) experience higher rates of negative mental health outcomes compared with their heterosexual peers; however, the association between sexual minority status and academic achievement is less clear. We used four waves of data from the National Longitudinal Study of Adolescent Health to compare 1,279 ethnically diverse SSAY (57% male) based on the degree to which they were “engaged” (65%) or “disengaged” (35%) in school, classified through cluster analysis techniques. The pattern of results indicated significantly better mental health among the engaged group one and 6 years later (e.g., fewer depressive symptoms, less alcohol use), and more occupational and educational achievement eleven years later. The implications of school connection and achievement across a decade of life are discussed.     

Out‐of‐School Time and Behaviors During Adolescence

Although adolescents experience an array of out‐of‐school time (OST) settings, research has primarily focused on these settings in isolation. This study examined time in four OST settings (unsupervised time with peers, paid employment, sports, and nonsports organized activities) in relation to adolescent functioning at age 15 and the end of high school. Individual fixed effects analyses provided a more rigorous control of selection into OST activities by controlling for time‐invariant observable and unobservable characteristics. More unsupervised time with peers predicted increases in risky and externalizing behaviors, whereas increases in paid employment predicted gains in work orientation and self‐identity. Time in organized sports was associated with increased positive self‐identity, highlighting the value of expanding consideration of multiple OST contexts and selection effects.