Finite mixture models with concomitant information: assessing diagnostic criteria for diabetes

The World Health Organization (WHO) diagnostic criteria for diabetes mellitus were determined in part by evidence that in some populations the plasma glucose level 2 h after an oral glucose load is a mixture of two distinct distributions. We present a finite mixture model that allows the two component densities to be generalized linear models and the mixture probability to be a logistic regression model. The model allows us to estimate the prevalence of diabetes and sensitivity and specificity of the diagnostic criteria as a function of covariates and to estimate them in the absence of an external standard. Sensitivity is the probability that a test indicates disease conditionally on disease being present. Specificity is the probability that a test indicates no disease conditionally on no disease being present. We obtained maximum likelihood estimates via the EM algorithm and derived the standard errors from the information matrix and by the bootstrap. In the application to data from the diabetes in Egypt project a two-component mixture model fits well and the two components are interpreted as normal and diabetes. The means and variances are similar to results found in other populations. The minimum misclassification cutpoints decrease with age, are lower in urban areas and are higher in rural areas than the 200 mg dl^-1 cutpoint recommended by the WHO. These differences are modest and our results generally support the WHO criterion. Our methods allow the direct inclusion of concomitant data whereas past analyses were based on partitioning the data.     

The context of correctness: A comment on rushton

According to Philippe Rushton, the equalitarian fiction, a scientific hoax that races are genetically equal in cognitive ability, underlies the politically correct objections to his research on racial differences. He maintains that there is a taboo against race unequaled by the Inquisition. I show that while Rushton has been publicly harassed, he has had continuous opportunities to present his findings in diverse, widely available, respectable journals, and no general suppression within academic psychology is evident. Similarly, Henry Garrett and his associates in the LAAEE, dedicated to preserving segregation and preventing race suicide, disseminated their ideas widely, although Garrett complained of the equalitarian fiction in 1961. Examination of the intertwined history ofMankind Quarterly, German Rassenhygiene, far right politics, and the work of Roger Pearson suggests that some cries of political correctness must be viewed with great caution.Preparation of this paper was not supported by any grant, foundation, political, or religious organization.specializing in the history of psychology and psychological aesthetics.     

Ability, disability, and the oldest old

A measure of range of ability is used to profile the 85-years-old-and-older (oldest old) population, including the highly disabled institutional population. This new measure uses two new questions available in the 1990 Decennial Census concerning a self-care limitation and a mobility limitation as well as the usual question concerning a work limitation. In addition to examining the extent of disability among the oldest old, the article examines the extent of care potentially available in the household as well as the economic characteristics of this age group. It is also profiled in terms of relevant personal characteristics, including age, gender, marital status, race, ethnicity, rural residence, education, and employment. A key question addressed is the need for help or care among the oldest old and how various long-term care proposals would meet such needs. A careful analysis of this unique and growing population is necessary to both allay fears of the cost of care or help as well as to dispel stereotypes of this age group as frail and dependent, and in need of institutional care.     

Planning for productivity

In the 1980s the subject of productivity will receive increasing attention as the old macro economic policies are replaced by micro economic policies. Everyone in various ways will discover the changes which will be involved in learning the real economic facts of life. The need to improve productivity and business performance is urgent and yet it is an area which is being neglected by management.     

The certainty of judgments in health evaluations

Most evaluators seem to presume that all evaluative studies should result in conclusive evidence. Often, however, less than conclusive evidence may not only suffice, but be the only real alternative under conditions of limited evaluation resources. Three levels of evidence common to evaluation studies are discussed: suggestive evidence, preponderant evidence, and conclusive evidence. Ten factors are also presented which can be used to determine the level of certainty appropriate for a given evaluation study. Consideration of these factors enables the evaluator to specify when less than conclusive evidence is acceptable.     

Public opinion and the privatization of welfare: some theoretical implications

The social policy of the Thatcher government is characterized by an abrupt shift in the direction of the private sector. To what extent does this reflect what people want? The Institute of Economic Affairs conclude from the only suitable national opinion survey that such a move is strongly supported. Our reanalysis of their data shows that this strand in public opinion can coexist with, and need not contradict, an equal public enthusiasm for state welfare. Such results have important implications for our understanding of social policy. We conclude, therefore, with a discussion of contrasting marxist and liberal accounts which seeks to show that the evidence of ambivalence in popular attitudes about the welfare state supports particular developments in theory.