Analytical approximations for iterated bootstrap confidence intervals

Standard algorithms for the construction of iterated bootstrap confidence intervals are computationally very demanding, requiring nested levels of bootstrap resampling. We propose an alternative approach to constructing double bootstrap confidence intervals that involves replacing the inner level of resampling by an analytical approximation. This approximation is based on saddlepoint methods and a tail probability approximation of DiCiccio and Martin (1991). Our technique significantly reduces the computational expense of iterated bootstrap calculations. A formal algorithm for the construction of our approximate iterated bootstrap confidence intervals is presented, and some crucial practical issues arising in its implementation are discussed. Our procedure is illustrated in the case of constructing confidence intervals for ratios of means using both real and simulated data. We repeat an experiment of Schenker (1985) involving the construction of bootstrap confidence intervals for a variance and demonstrate that our technique makes feasible the construction of accurate bootstrap confidence intervals in that context. Finally, we investigate the use of our technique in a more complex setting, that of constructing confidence intervals for a correlation coefficient.     

Psychosocial adaption to pregnancy in prison.

1. Childbearing for incarcerated women is complicated by characteristics of special needs associated with psychosocial adaptation to increased stress, a restrictive physical environment, alteration of social support systems, and the displacement of the maternal role functions after birth. 2. Psychiatric nurses are in a unique position to affect the health care provided for pregnant inmates by virtue of their knowledge and expertise in assessing and treating problems in psychosocial adaptation. 3. Assessment of pregnant inmates is based on identification of the presence and magnitude of dimensions of stress, environmental restrictiveness, social support systems, and maternal role displacement.     

The role of family help in the housing decisions of young people

Recent debates about flows of help within the family have indicated considerable diversity according to the type of help (money, services), and ages and gender of those involved, and have shown that values are only a partial guide to the scale of such flows. This paper focuses on a particular occasion for help, young people's housing, and a particular region, South-East England, where one would expect family financial help to be high given the capacity to help of older generations (due to higher average incomes and wealth) and the affordability problems faced by young people. It is shown that contrary to hypothesis only 12% of a sample of young people had received financial help for housing purposes since they had left home, less than found in previous studies with different samples. The amounts involved were less than young people believed their parents could afford. The role of inheritance was also found to be minor. The results from the different studies are explained as due to changes in the housing market, changing values regarding financial help and differences among the samples. Intensive re-interviews with three households from very different backgrounds are used to show the different ways in which family help operates.     

Is there a field of social work?: Trainees evaluating social problems and social work

My aim was to study the experiences and priorities of two age groups of social work students practicing in client-centered social work. This article is based on the research on rationality and language games in social work. The target groups of the research project as a whole were the actors: the heads and social workers or activists in public social welfare and health care agencies and institutions and in voluntary associations and action groups, and finally, two subsequent classes of students from a school of social work, during their practicing periods. This article concentrates on the trainees. At first, the trainees wrote essays and kept diaries. Secondly, they marked their standings on graphs visualizing different types of information contents and social relation structures. Thirdly, they made their choices of reasons for and solutions to social problems on a problem wheel. The trainees' study, using different data gathering techniques, partly confirms the results of the research of the other actor groups, in which the data were derived using questionnaires and interviews. The trainees' study shows variation in the respondents' priorities within and between specified social problem categories. Qualitatively analyzed, however, the characterizations of social work, both those who currently act in and those aiming to enter this field, resemble one another.     

INNUMERACY ABOUT MINORITY POPULATIONS

We use a small but nationally representative sample to investigatethe sources of innumeracy regarding the proportion of blacks,Hispanics, and Jews in the U.S. population. In addition to anumber of standard demographic differences, we find that overestimatesare closely related to region as well as to the density of thelocal black/Hispanic population. The extent to which minoritypopulations are perceived as a kind of threat is also relatedto perceived proportions, though the direction of causalitycannot be determined. We discuss the meaningfulness of thesepopulation estimates and speculate on whether trying to improvethem would alter attitudes toward minorities.     

Exposure Reconstruction for the TCDD-Exposed NIOSH Cohort Using a Concentration- and Age-Dependent Model of Elimination

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.     

A Numerical Solution to the Nonhomogeneous Two-Stage MVK Model of Cancer

In this article, we describe a straightforward method for solving the probability of at least one malignant cell by time t, and the associated hazard function, in the general (i.e., nonhomogeneous) two-stage Moolgavkar-Venzon-Knudson (MVK) model of cancer. The method consists of solving four coupled ordinary differential equations derived from the Kolmogorov backward equations for this process. The relationship of this method to previously proposed solutions is discussed.     

中国蒙古文学史料学的起始与发展

蒙古文学研究的基础和前提是蒙古文学史料。随着国内外蒙古文学研究的不断拓展和深入,蒙古文学史料搜集整理已逐步发展成为蒙古文学史料学。蒙古文学史料学包括蒙古文学的田野调查、史料整理、考订、选录、笺释、校注、校勘、辑评等诸多研究内涵。中国蒙古文学研究取得巨大成就,得益于蒙古文学史料学的长足发展。我们应当总结以往蒙古文学史料学研究的经验,使蒙古文学史料学更加系统化、科学化和理论化。     

The impact of social networks on the occupational status of migrants

This paper postulates that there is a continuous exchange of information and knowledge between those who share the common bond of having migrated to the US. The individual components of this information exchange constitute social networks. The 2 hypotheses tested are 1) immediate social networks and people known in the US facilitate the flow of information both to new migrants and between established migrants, thus promoting upward social mobility; and 2) access to broader network ties, organization membership, extra-ethnic friendships, and familiarity with established institutions smooths the transition process, resulting in increased social position. The data used comes from a study conducted in 1982-1983 in 4 Mexican sending communities (2 rural, 2 urban), for a total of 440 migrants. Results show that migrants in every socioeconomic bracket reported access to some or all social network characteristics. There was contact with either a family member or acquaintances from the migrants' town of origin. Over 50% of migrants reported knowing many fellow townspeople. Twice as many migrants belong to a sports club as to a social or religious organization. Very few rural migrants report knowing no townspeople, while 32% of urban migrants claim no knowledge of fellow migrants from their town of origin. Urban origin migrants report more contacts with those of other ethnicity than rural migrants. Those employed in agriculture are least acquainted with social information and contacts, while those in skilled and service sectors are well acquainted with them. The results of fact and analysis show that 1) access to personal US networks results in an average 4.4 point advantage in occupational prestige scores over no access, and 2) utilizing institutional US networks combined with any cumulative US experience gives a migrant a 5 point advantage over a fellow migrant with identical experience level but no institutional network contacts. This is also true for institutional Mexican networks. Thus success or failure in migrating is partly due to migrants' societal infrastructure and the fact that available information and social networks are accessed and utilized differently by different migrants.