Kernel Smoothing Density Estimation when Group Membership is Subject to Missing

Density function is a fundamental concept in data analysis. Non-parametric methods including kernel smoothing estimate are available if the data is completely observed. However, in studies such as diagnostic studies following a two-stage design the membership of some of the subjects may be missing. Simply ignoring those subjects with unknown membership is valid only in the MCAR situation. In this paper, we consider kernel smoothing estimate of the density functions, using the inverse probability approaches to address the missing values. We illustrate the approaches with simulation studies and real study data in mental health.     

An improved ranked set two‐sample mann‐whitney‐wilcoxon test

The authors present an improved ranked set two‐sample Mann‐Whitney‐Wilcoxon test for a location shift between samples from two distributions F and G. They define a function that measures the amount of information provided by each observation from the two samples, given the actual joint ranking of all the units in a set. This information function is used as a guide for improving the Pitman efficacy of the Mann‐Whitney‐Wilcoxon test. When the underlying distributions are symmetric, observations at their mode(s) must be quantified in order to gain efficiency. Analogous results are provided for asymmetric distributions.     

Racial Formation in Theory and Practice: The Case of Mexicans in the United States

Mechanisms of social stratification require the categorical definition of an out-group to that can be excluded and exploited. Historically, in the United States, African Americans have been the subject of a systematic process of racial formation to define socially in this fashion. Beginning in the 1970s, however, and accelerating in the 1980s and 1990s, Mexicans were increasingly subject to processes of racialization that have rendered them more exploitable and excludable than ever before. Over the past decade, Mexican Americans moved steadily away from their middle position in the socioeconomic hierarchy and gravitated toward the bottom. This paper describes the basic mechanisms of stratification in the United States and how Mexicans have steadily been racialized to label them socially as a dehumanized and vulnerable out-group.     

Robust designs for misspecified logistic models

We develop criteria that generate robust designs and use such criteria for the construction of designs that insure against possible misspecifications in logistic regression models. The design criteria we propose are different from the classical in that we do not focus on sampling error alone. Instead we use design criteria that account as well for error due to bias engendered by the model misspecification. Our robust designs optimize the average of a function of the sampling error and bias error over a specified misspecification neighbourhood. Examples of robust designs for logistic models are presented, including a case study implementing the methodologies using beetle mortality data.     

Evaluating bias correction in weighted proportional hazards regression

Often in observational studies of time to an event, the study population is a biased (i.e., unrepresentative) sample of the target population. In the presence of biased samples, it is common to weight subjects by the inverse of their respective selection probabilities. Pan and Schaubel (Can J Stat 36:111–127, 2008) recently proposed inference procedures for an inverse selection probability weighted (ISPW) Cox model, applicable when selection probabilities are not treated as fixed but estimated empirically. The proposed weighting procedure requires auxiliary data to estimate the weights and is computationally more intense than unweighted estimation. The ignorability of sample selection process in terms of parameter estimators and predictions is often of interest, from several perspectives: e.g., to determine if weighting makes a significant difference to the analysis at hand, which would in turn address whether the collection of auxiliary data is required in future studies; to evaluate previous studies which did not correct for selection bias. In this article, we propose methods to quantify the degree of bias corrected by the weighting procedure in the partial likelihood and Breslow-Aalen estimators. Asymptotic properties of the proposed test statistics are derived. The finite-sample significance level and power are evaluated through simulation. The proposed methods are then applied to data from a national organ failure registry to evaluate the bias in a post-kidney transplant survival model.     

Linear and Nonlinear Valence Functions: A Behavioral Decision-Making Assessment

In Vroom's [45] original formulation of expectancy theory, the relationship between affect and perceived instrumentality was assumed to be linear. Others have suggested that such a relationship may be better modeled by a nonlinear, utility-type function [30]. The current research contrasts the predictive ability of two linear and four nonlinear functions. Using four levels of McClelland's [26] needs for achievement, affiliation, and power as instrumentalities, 101 subjects provided more than 12,900 decisions on the valences of jobs in a behavioral decision-making experiment. Nearly 40 percent of the subjects exhibited nonlinear valence functions. The results emphasize the need to specify the appropriate functional form of the valence component to enhance predictive accuracy and to prevent misspecification problems.     

Competing risk analysis in a large cardiovascular clinical trial: An APEX substudy

Competing risk methods are time‐to‐event analyses that account for fatal and/or nonfatal events that may potentially alter or prevent a subject from experiencing the primary endpoint. Competing risk methods may provide a more accurate and less biased estimate of the incidence of an outcome but are rarely applied in cardiology trials. APEX investigated the efficacy of extended‐duration betrixaban versus standard‐duration enoxaparin to prevent a composite of symptomatic deep‐vein thrombosis (proximal or distal), nonfatal pulmonary embolism, or venous thromboembolism (VTE)–related death in acute medically ill patients (n = 7513). The aim of the current analysis was to determine the efficacy of betrixaban vs standard‐duration enoxaparin accounting for non‐VTE–related deaths using the Fine and Gray method for competing risks. The proportion of non‐VTE–related death was similar in both the betrixaban (133, 3.6%) and enoxaparin (136, 3.7%) arms, P = .85. Both the traditional Kaplan‐Meier method and the Fine and Gray method accounting for non‐VTE–related death as a competing risk showed equal reduction of VTE events when comparing betrixaban to enoxaparin (HR/SHR = 0.65, 95% 0.42‐0.99, P = 0.046). Due to the similar proportion of non‐VTE–related deaths in both treatment arms and the use of a univariate model, the Fine and Gray method provided identical results to the traditional Cox model. Using the Fine and Gray method in addition to the traditional Cox proportional hazards method can indicate whether the presence of a competing risk, which is dependent of the outcome, altered the risk estimate.     

Delivering decision making support to people with cognitive disability — What has been learned from pilot programs in Australia from 2010 to 2015

The UNCRPD has generated debate about supported decision making as a way to better enable people with cognitive disability to participate in decision making. In Australia, between 2010–2015, a series of projects have piloted various models of delivering decision making support. A critical review was conducted on the program documents and evaluations of these pilot projects. The pilots were small scale, conducted by both statutory and non‐statutory bodies, and adopted similar designs centred on supporting a decision maker/supporter dyad. Primarily, participants were people with mild intellectual disability. Themes included: positive outcomes; uncertain boundaries of decision support; difficulty securing supporters; positive value of program staff and support to supporters; limited experience and low expectations; and varying value of written resources. The lack of depth and rigour of evaluations mean firm conclusions cannot be reached about program logics, costs or outcomes of the pilots. The pilots demonstrate feasibility of providing support for decision making rather than resolving issues involved in delivering support. They suggest that some form of authority may facilitate the role of decision supporters, help to engage others in a person's life, and integrate decision making support across all life domains.     

Family structure and the reproduction of inequality: Parents’ contribution to children’s college costs

This article examines the role of family structure in the financial support parents provide for their children’s college education. Data are from the Health and Retirement Study. We focus on aspects of family structure that affect parental support and estimate shared family variance in investments as well as within-family variation using a multilevel model. Family membership accounts for about 60% of the variance in payment of college costs. Small family size, living with both biological parents (compared to one biological parent and a stepparent), higher parental education, and having older parents are associated with greater parental expenditures.     

Pathways to El Norte: origins, destinations, and characteristics of Mexican migrants to the United States

The geography Mexican migration to the U.S. has experienced deep transformations in both its origin composition and the destinations chosen by migrants. To date, however, we know little about how shifting migrant origins and destinations may be linked to each another geographically and, ultimately, structurally as relatively similar brands of economic restructuring have been posited to drive the shifts in origins and destinations. In this paper, we describe how old and new migrant networks have combined to fuel the well-documented geographic expansion of Mexican migration. We use data from the 2006 Mexican National Survey of Population Dynamics, a nationally representative survey that for the first time collected information on U.S. state of destination for all household members who had been to the U.S. during the 5 years prior to the survey. We find that the growth in immigration to southern and eastern states is disproportionately fueled by undocumented migration from non-traditional origin regions located in Central and Southeastern Mexico and from rural areas in particular. We argue that economic restructuring in the U.S. and Mexico had profound consequences not only for the magnitude but also for the geography of Mexican migration, opening up new region-to-region flows.