The analysis of incomplete data using stochastic covariates

In the development of many diseases there are often associated random variables which continuously reflect the progress of a subject towards the final expression of the disease (failure). At any given time these processes, which we call stochastic covariates, may provide information about the current hazard and the remaining time to failure. Likewise, in situations when the specific times of key prior events are not known, such as the time of onset of an occult tumour or the time of infection with HIV-1, it may be possible to identify a stochastic covariate which reveals, indirectly, when the event of interest occurred. The analysis of carcinogenicity trials which involve occult tumours is usually based on the time of death or sacrifice and an indicator of tumour presence for each animal in the experiment. However, the size of an occult tumour observed at the endpoint represents data concerning tumour development which may convey additional information concerning both the tumour incidence rate and the rate of death to which tumour-bearing animals are subject. We develop a stochastic model for tumour growth and suggest different ways in which the effect of this growth on the hazard of failure might be modelled. Using a combined model for tumour growth and additive competing risks of death, we show that if this tumour size information is used, assumptions concerning tumour lethality, the context of observation or multiple sacrifice times are no longer necessary in order to estimate the tumour incidence rate. Parametric estimation based on the method of maximum likelihood is outlined and is applied to simulated data from the combined model. The results of this limited study confirm that use of the stochastic covariate tumour size results in more precise estimation of the incidence rate for occult tumours.     

HIV-infected woman. Illness cognition assessment.

1. Special attention is particularly important in addressing the mental health needs of HIV-infected women. These needs may involve issues such as concerns about present or future pregnancy; child-rearing, often as single parents; poverty, illicit drug use or addiction; and the potential lack of support services. 2. Diagnosis of HIV infection in women may be overlooked, as the clinical signs that routinely trigger the suspicion of HIV illness in men are often interpreted to reflect depression or psychological factors, such as stress or overwork, rather than raise the suspicion of HIV infection in women. 3. Understanding a woman's illness cognition is an important component of designing strategies that can enhance coping. The picture a woman generates regarding her illness is a composite of her experiences and responses, and determines to a large extent what she will do in response to her illness.     

Procedures and tables for the construction and selection of chain sampling plans ChSP-4A(c1, c2,)r-Part 4

In this part of the series, the notion of average total inspection (ATI) is introduced to ChSP-4A(c1, c2)r plans, minimizing ATI at a given process average, while protection to the consumer is given in terms of average outgoing quality limit and limiting quality level. The procedure is similar to that of Dodge and Roming.     

The dilemma of recognition: Administrative categories and cultural diversity

Governments around the world combat inequality by means of group-specific redistribution. Some pursue redistribution that benefits groups, but also wish to avoid accentuating or even recognizing group distinctions. This poses a dilemma that they try to resolve by adjusting the category system used to target redistribution. There are three types of adjustment: accommodation (the multicultural approach), denial (the ideal-typical liberal solution), and replacement (a compromise). In replacement the targets of redistributive policies are constructed to avoid accentuation or recognition of inconvenient group distinctions, but still allow redistribution that benefits these groups. Replacement is increasingly in demand around the world because the disadvantages of multiculturalism are becoming apparent while denial is hard to sustain in the face of group inequality. The actual effect of replacement is little researched and less understood, however. Does it resolve the dilemma of recognition? Two examples–India and Nigeria–where replacement has been tried ever since the 1950s cast doubt on its viability.     

African American Migration to the North: New Evidence for the 1910s

The years between 1910 and 1920 witnessed the first wave of the "Great Migration" of African Americans to the North. This article uses new census data from the Integrated Public Use Microdata Series project to study self‐selection patterns in African American migration during this important decade. The results indicate that, contrary to contemporary accounts, migration rates rose at least as much among the literate as among the illiterate (and perhaps more), and migration increased more for married African Americans than for the unmarried.     

Bilingual Education Models in Latvia: A view from Belarus

In this article, we look at several issues relating to bilingual education in Latvia, as prescribed by the Latvian Ministry of Education and Science. We examine these issues from the perspective of the past and present situation in Belarus, Russia and the former Soviet Union. It is clear, in our view, that bilingual offers both advantages, but also various drawbacks if it is not implemented in an appropriate way. This applies to both the societal and the personal (cognitive level). Movement towards the dominant languages (in this case Latvian) needs to be viewed as a gradual process. Although each generation of newcomers might start with a passive knowledge of the dominant (second) language, this changes into a fluent grasp of the second language across generations. The original native language will lose its dominance in this process.     

Characterizations of gamma,inverse Gaussian,and negative binomial distributions via their length-biased distributions

A general form for characterizing inverse Gaussian and Wald distributions, based on their respective length-biased distributions, is introduced. Further results for characterizations of the gamma distribution, the negative binomial distribution and some mixtures of them by using their lengthbiased distributions are establised.