An investigation of racial and ethnic disparities in birth weight in Chicago neighborhoods

We examine differences in the mean birth weights of infants born to non-Hispanic black, non-Hispanic white, and Mexican-origin Hispanic mothers (of any race) in Chicago in 1990 using linear regression models with neighborhood fixed effects. Our pooled models accounted for 64% of the black-white difference and 57% of the black/Mexican-origin Hispanic difference. Differences in the relationship between measured characteristics and birth weight accounted for around half the birth-weight gap between non-Hispanic black and other infants. Efforts to close this gap must go beyond programs that aim to reduce the level of risk factors among black women to address the causes of differences in the effects of risk factors.     

Uncertainty Quantification in the Ensemble Kalman Filter

The ensemble Kalman filter (EnKF) provides an approximate, sequential Monte Carlo solution to the recursive data assimilation algorithm for hidden Markov chains. The challenging conditioning step is approximated by a linear updating, and the updating weights, termed Kalman weights, are inferred from the ensemble members. The EnKF scheme is known to provide unstable predictions and to underestimate the prediction intervals, and even sometimes to diverge. The underlying cause for these shortcomings is poorly understood. We find that the ensemble members couple in the conditioning procedure and that the coupling increase multiplicatively in the recursive conditioning steps. Under reasonable Gauss‐independence assumptions, exact expressions for this correlation are developed. Moreover, expressions for the precision of the predictions and the downward bias in the empirical variance introduced in one conditioning step are found. These results are confirmed by a Gauss‐linear simulation study. Furthermore, we quantitatively evaluate an alternative, improved EnKF scheme on the basis of transformations of ensemble members under the same Gauss‐independent assumptions. The scheme is compared with the frequently used ensemble inflation scheme.     

Ecological regression analysis of environmental benzene exposure and childhood leukaemia: sensitivity to data inaccuracies, geographical scale and ecological bias

Benzene is classified as a group 1 human carcinogen by the International Agency for Research on Cancer, and it is now accepted that occupational exposure is associated with an increased risk of various leukaemias. However, occupational exposure accounts for less than 1% of all benzene exposures, the major sources being cigarette smoking and vehicle exhaust emissions. Whether such low level exposures to environmental benzene are also associated with the risk of leukaemia is currently not known. In this study, we investigate the relationship between benzene emissions arising from outdoor sources (predominantly road traffic and petrol stations) and the incidence of childhood leukaemia in Greater London. An ecological design was used because of the rarity of the disease, the difficulty of obtaining individual level measurements of benzene exposure and the availability of data. However, some methodological difficulties were encountered, including problems of case registration errors, the choice of geographical areas for analysis, exposure measurement errors and ecological bias. We use a Bayesian hierarchical modelling framework to address these issues, and we investigate the sensitivity of our inference to various modelling assumptions.     

Likelihood Ratio Testing for Hidden Markov Models Under Non-standard Conditions

Abstract.  In practical applications, when testing parametric restrictions for hidden Markov models (HMMs), one frequently encounters non-standard situations such as testing for zero entries in the transition matrix, one-sided tests for the parameters of the transition matrix or for the components of the stationary distribution of the underlying Markov chain, or testing boundary restrictions on the parameters of the state-dependent distributions. In this paper, we briefly discuss how the relevant asymptotic distribution theory for the likelihood ratio test (LRT) when the true parameter is on the boundary extends from the independent and identically distributed situation to HMMs. Then we concentrate on discussing a number of relevant examples. The finite-sample performance of the LRT in such situations is investigated in a simulation study. An application to series of epileptic seizure counts concludes the paper.     

Defining and Estimating the Scope of U.S. Faith-Based International Humanitarian Aid Organizations

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - This study illuminates the size, scope, and impact of U.S. faith-based nonprofits in the international affairs sector....     

Southern Romance: Relationship Quality,Consensus, and Context among Cohabiting Couples in the Gulf States

Abstract

Relationships are significantly stressed in the Southeastern United States. Of the six states in the Gulf region (Florida, Georgia, Alabama, Mississippi, Louisiana, and Texas), four are in the top-third of the nation's highest divorce rates. Threats to relationship household stability cause a myriad of social problems and public expenses of approximately $24 billion in increased spending in benefit programs to offset family hardship following divorce and relationship dissolution. This study analyzed associations between relationship quality and satisfaction, consensus, and a series of contextual variables among three types of cohabiting homeowners across the Gulf States (unmarried, married, and married with additional family members), surveying variables of interest. Findings indicated that dyadic couple relationships in this sample are generally distressed relative to other states and that significant negativity is present, but that a large portion of the variance in relationship quality is consistently predicted by certain factors. Using an instrument of increased sensitivity, these factors (consensus, negative interaction, household composition, etc.) have been parsed into specific components (types of consensus, types of interaction, etc.) for improved individual analysis. Specific relationship problem areas are outlined, clarified, and discussed.     

Toward a theory of myth

James Cresswell provides a thoughtful critique of my essay on a theory of myth (Mills) with a specific focus on the nature of theorizing that challenges the dogma of empirical frames of reference, concluding that scientific theories themselves are contemporary myths. Insofar as myth is an attempt to provide a narrative or discourse about phenomena, Cresswell's argument could apply to any theory. But he takes this point further: theory is synonymous with myth. In order to unpack this evocative claim, it may prove useful to revisit how theory and myth relate to the concepts of logos, truth, ontology and identity. In the end, I suggest theory is not myth because theory sets out to describe, interpret and explain phenomena and is scrutinized for its validity, generalizability and applied consequences, while the premises of myth are often historically and culturally presupposed or simply devolve into belief that may or may not be defensible.     

Planning Forward by Looking Backward: Retrospective Thinking in Strategic Decision Making*

Retrospective thinking occurs whenever one remembers something from the past, but one can also think retrospectively about hypothetical future events, by imagining that the event has already transpired and then working backward in the mind from the future toward the present. Designers, artists, planners, and other creative individuals utilize retrospective thinking when they mentally envision the object they wish to create and then thinkabout how it might be constructed. Some theorists and some previous research have suggested that forward and backward thinking are different cognitive processes, but there has been little investigation on the nature of these differences. This article examines the literature and describes a laboratory study designed to investigate retrospective thinking as a technique for increased idea generation. Subjects (n=64) were professional planners and managers with an average business experience of over 20 years. In a planning task, significantly more ideas were generated in the retrospective thinking mode than in the prospective mode, but the ideas were not found to be of greater quality. Evidence emerged that a subset of subjects were better able to make use of the retrospective technique, suggesting that selection along with training may be appropriate for the technique's mosteffective use.