Commissioned analysis of surgical performance using routine data: lessons from the Bristol inquiry

The public inquiry into paediatric cardiac surgery at the Bristol Royal Infirmary commissioned the authors to design and conduct analyses of routine data sources to compare surgical outcomes between centres. Such analyses are necessarily complex in this context but were further hampered by the inherent inconsistencies and mediocre quality of the various sources of data. Three levels of analysis of increasing sophistication were carried out. The reasonable consistency of the results arising from different sources of data, together with a number of sensitivity analyses, led us to conclude that there had been excess mortality in Bristol in open heart operations on children under 1 year of age. We consider criticisms of our analysis and discuss the role of statisticians in this inquiry and their contribution to the final report of the inquiry. The potential statistical role in future programmes for monitoring clinical performance is highlighted.     

Bayesian analysis of the scatterometer wind retrieval inverse problem: some new approaches

Summary.  The retrieval of wind vectors from satellite scatterometer observations is a non-linear inverse problem. A common approach to solving inverse problems is to adopt a Bayesian framework and to infer the posterior distribution of the parameters of interest given the observations by using a likelihood model relating the observations to the parameters, and a prior distribution over the parameters. We show how Gaussian process priors can be used efficiently with a variety of likelihood models, using local forward (observation) models and direct inverse models for the scatterometer. We present an enhanced Markov chain Monte Carlo method to sample from the resulting multimodal posterior distribution. We go on to show how the computational complexity of the inference can be controlled by using a sparse, sequential Bayes algorithm for estimation with Gaussian processes. This helps to overcome the most serious barrier to the use of probabilistic, Gaussian process methods in remote sensing inverse problems, which is the prohibitively large size of the data sets. We contrast the sampling results with the approximations that are found by using the sparse, sequential Bayes algorithm.     

Poorer Is Riskier

To examine the relationship between economic well being and health status, two economic concepts were explored: the permanent-income hypothesis and the transitory-income hypothesis. A regression analysis of time-series mortality data for the period of 1950-1988 was conducted. The regression results indicated that the total mortality rate is negatively associated with permanent income and positively associated with the transitory income. Results are also reported for the 8 major causes of death in the United States. The implications for risk analysis are discussed.     

General Deterrence of Drunk Driving: Evaluation of Recent American Policies

A testable hypothesis of deterrence theory is that efforts to increase the expected cost of criminal activity by increasing the threat of punishment should, other things being equal, reduce the crime rate. In this paper, we examine whether the incidence of drinking and driving is responsive to escalation of the punitive threat. The recent national campaign against drunk driving provides a natural experiment in which to test the predictions of deterrence theory. Using state level data over the 1975-1986 period, we report no conclusive evidence that any specific form of punitive legislation is having a measurable effect on motor vehicle fatalities. We report suggestive evidence that multiple laws designed to increase the certainty of punishment (e.g., sobriety checkpoints and preliminary breath tests) have a synergistic deterrent effect. The most striking finding is that mandatory seat belt use laws and beer taxes may be more effective at reducing drunk driving fatalities than policies aimed at general deterrence.     

The Effect of Neglecting Correlations When Propagating Uncertainty and Estimating the Population Distribution of Risk

Interest in examining both the uncertainty and variability in environmental health risk assessments has led to increased use of methods for propagating uncertainty. While a variety of approaches have been described, the advent of both powerful personal computers and commercially available simulation software have led to increased use of Monte Carlo simulation. Although most analysts and regulators are encouraged by these developments, some are concerned that Monte Carlo analysis is being applied uncritically. The validity of any analysis is contingent on the validity of the inputs to the analysis. In the propagation of uncertainty or variability, it is essential that the statistical distribution of input variables are properly specified. Furthermore, any dependencies among the input variables must be considered in the analysis. In light of the potential difficulty in specifying dependencies among input variables, it is useful to consider whether there exist rules of thumb as to when correlations can be safely ignored (i.e., when little overall precision is gained by an additional effort to improve upon an estimation of correlation). We make use of well-known error propagation formulas to develop expressions intended to aid the analyst in situations wherein normally and lognormally distributed variables are linearly correlated.     

Partial Paradigm Shifts in the Social Sciences: Twenty Years of Research in Rural Sociology3

Abstract Falk and Zhao (1989) have recently suggested that increased theoretical diversity characterizes the last decade of published research in Rural Sociology. We suggest that this claim is premature, given paradigmatic trends in the larger discipline of sociology. From a reanalysis of data sources and the use of an analytical framework based on the partial paradigm concept, we conclude that rural sociology is attempting to further integrate theory, methodology, and image of the subject matter within a positivistic partial paradigm framework. We further suggest that rural sociologists continue their pursuit of a reflexive understanding of the practice of social science as an integral part of their research agenda.     

A suggested framework for analysis of urban-rural fertility differentials with an illustration of the Tanzanian case

This paper offers a framework for analyzing how individual characteristics and urban or rural "place" factors interact to influence fertility decisions. The framework builds on the Davis-Blake model and additionally shows how place or community variables influence exposure to intercourse, conception, and birth, either with or without a conscious decisionmaking process. The framework emphasizes the way person and place related factors combine to determine a woman's perception of her life options before bearing any children, as well as how changes in these factors may affect subsequent child decisions. The framework is briefly illustrated by the Tanzanian case. The analysis highlights urban-based considerations, such as education-wage differentials, which may influence the rural couple's decisions. A comparison of two rural cohorts shows that specific community variables such as cultural attitudes, accessibility, general educational levels, and child mortality mediate the influence of these urban-based phenomena.Research for this project was completed while the author was affiliated with GETEMPO, Washington, D.C., under contract to the Office of Urban Development, U.S. Agency for International Development. The author gratefully acknowledges the comments and assistance of Ann C. Orr, James E. Kocher, Paula E. Hollerbach, and two anonymous referees. Requests for reprints should be directed to Sally Evans Findley, Minnesota State Planning Agency, Room 101 Capitol Square Building, 550 Cedar Street, St. Paul, Minnesota 55101.     

Social Networks,Migration, and Care in Tanzania

This paper explores the impacts of the HIV/AIDS epidemic on children and families in northern Tanzania using the concept of social resilience.1 1. This paper is based on a presentation entitled, “Social Networks, Migration and Care in Tanzania: Supporting Women, Children and Young People's Resilience,” prepared for the 2nd African Conference on the Social Aspects of HIV/AIDS Research, International Convention Centre, Cape Town, May 9–12, 2004, organized by the Human Sciences Research Council, South Africa (see: www.sahara.org.za). View all notes The study is based on the findings of child-focused research with street children and children and families from HIV/AIDS-affected households. The paper illustrates the coping strategies that children and young people, and parents and caregivers adopt at the household level. In particular, it examines how the burden of care affects different generations of women and highlights their resilience, together with the importance of social networks and the fluidity of movement between rural and urban areas. The research suggests that migrating to urban areas to seek a living in the informal sector represents a survival strategy adopted by some children and young people orphaned by AIDS when their families and communities are unable or unwilling to support them. The paper concludes by exploring parents’, caregivers’, children's, and young people's views on the forms of social support that would promote their resilience and thereby help to mitigate the impacts of the epidemic at the household level.     

The Importance of Race Among Black Sociologists*

This paper explores the importance of race and racial attitudes among sociologists by attempting to document the existence of what has been called a “black insiders doctrine” and showing that black sociologists are more likely than their white counterparts to subscribe to this doctrine. Data in this paper are based on a survey questionnaire administered during the winter of 1978. The findings show that: (1) race is a strong predictor in determining how sociologists perceive the role and characteristics of black sociologists and (2) black sociologists do not think highly of whites who study race relations.