Direct parametric inference for the cumulative incidence function

Summary.  In survival data that are collected from phase III clinical trials on breast cancer, a patient may experience more than one event, including recurrence of the original cancer, new primary cancer and death. Radiation oncologists are often interested in comparing patterns of local or regional recurrences alone as first events to identify a subgroup of patients who need to be treated by radiation therapy after surgery. The cumulative incidence function provides estimates of the cumulative probability of locoregional recurrences in the presence of other competing events. A simple version of the Gompertz distribution is proposed to parameterize the cumulative incidence function directly. The model interpretation for the cumulative incidence function is more natural than it is with the usual cause-specific hazard parameterization. Maximum likelihood analysis is used to estimate simultaneously parametric models for cumulative incidence functions of all causes. The parametric cumulative incidence approach is applied to a data set from the National Surgical Adjuvant Breast and Bowel Project and compared with analyses that are based on parametric cause-specific hazard models and nonparametric cumulative incidence estimation.     

Exposure Factors for Wastewater‐Irrigated Asian Vegetables and a Probabilistic Rotavirus Disease Burden Model for Their Consumption

Many farmers in water‐scarce regions of developing countries use wastewater to irrigate vegetables and other agricultural crops, a practice that may expand with climate change. There are a number of health risks associated with wastewater irrigation for human food crops, particularly with surface irrigation techniques common in the developing world. The World Health Organization (WHO) recommends using quantitative microbial risk assessment (QMRA) to determine if the irrigation scheme meets health standards. However, only a few vegetables have been studied for wastewater risk and little information is known about the disease burden of wastewater‐irrigated vegetable consumption in China. To bridge this knowledge gap, an experiment was conducted to determine volume of water left on Asian vegetables and lettuce after irrigation. One hundred samples each of Chinese chard (Brassica rapa var. chinensis), Chinese broccoli (Brassica oleracea var. alboglabra), Chinese flowering cabbage (Brassica rapa var. parachinensis), and lettuce (Lactuca sativa) were harvested after overhead sprinkler irrigation. Chinese broccoli and flowering cabbage were found to capture the most water and lettuce the least. QMRAs were then constructed to estimate rotavirus disease burden from consumption of wastewater‐irrigated Asian vegetables in Beijing. Results indicate that estimated risks from these reuse scenarios exceed WHO guideline thresholds for acceptable disease burden for wastewater use, signifying that reduction of pathogen concentration or stricter risk management is necessary for safe reuse. Considering the widespread practice of wastewater irrigation for food production, particularly in developing countries, incorporation of water retention factors in QMRAs can reduce uncertainty regarding health risks for consumers worldwide.     

Reviewing the latest national policies and services for people with severe mental health disorders in government-funded institutions in Vietnam,and policy recommendations for service improvements

The aim of this paper is to provide the international community with a broad and updated picture of key policies and services for people with severe mental health disorders in Vietnam. In particular, the paper (1) reviews the most important national policies governing care for people with mental health disorders, (2) reviews the status of free-of-charge care provided to people with severe mental health disorders in a network of government-funded facilities across the nation and (3) discusses the future policy directions of Vietnam regarding people with mental health disorders.     

Social networks among lower income Korean elderly immigrants in the U.S.

This study examines the composition and cultural context of the social networks of a sample of primarily lower-income Korean elderly immigrants and the resources and supports available through those network ties. In-depth, in-person interviews were used to investigate categories of network ties and the nature of network exchanges. Non-kin and organizational contacts were primary sources of emotional and instrumental support among this sample, with the norms and institutions of elder care in the U.S. shaping expectations regarding sources of support.     

A note on the asymptotic relative efficiency of estimators from the additive hazards model

In this note, the asymptotic variance formulas are explicitly derived and compared between the parametric and semiparametric estimators of a regression parameter and survival probability under the additive hazards model. To obtain explicit formulas, it is assumed that the covariate term including a regression coefficient follows a gamma distribution and the baseline hazard function is constant. The results show that the semiparametric estimator of the regression coefficient parameter is fully efficient relative to the parametric counterpart when the survival time and a covariate are independent, as in the proportional hazards model. Relative to a more realistic case of the parametric additive hazards model with a Weibull baseline, the loss of efficiency of the semiparametric estimator of survival probability is moderate.     

Goodness-of-fit test for density estimation

It is often necessary to test whether X,…, X_n are from a certain density f(x) or not. Most test statistics such as the Kolmogorov-Smirnov, Cramer-von Mises, and Anderson-Darling statistics are based on the empirical distribution function F(x). In this paper we suggest a test statistic based on the integrated squared error of the kernel density estimator. We derive the asymptotic distribution of the statistic under the null and alternative hypothesis. Some simulation results for power comparisons are also given.     

Quality of Life Across Life Domains: Family Structure and Relations

Social Indicators Research - This paper aims to evaluate how the Korean family fares in terms of itsquality of life. Specifically, it examines the perceived quality of relationships among family...     

Strategy-proof rules for two public goods: double median rules

We consider the problem of selecting the locations of two (identical) public goods on an interval. Each agent has preferences over pairs of locations, which are induced from single-peaked rankings over single locations: each agent compares pairs of locations by comparing the location he ranks higher in each pair. We introduce a class of “double median rules” and characterize it by means of continuity, anonymity, strategy-proofness, and users only. To each pair of parameter sets, each set in the pair consisting of $(n+1)$ parameters, is associated a rule in the class. It is the rule that selects, for each preference profile, the medians of the peaks and the parameters belonging to each set in the pair. We identify the subclasses of the double median rules satisfying group strategy-proofness, weak efficiency, and double unanimity (or efficiency), respectively. We also discuss the classes of “multiple median rules” and “non-anonymous double median rules”.     

A Model of Family Background,Family Process,Youth Self-Control,and Delinquent Behavior in Two-Parent Families

Using data from a national sample of two-parent families with 11- and 12-year-old youths (N = 591), we tested a structural model of family background, family process (marital conflict and parenting), youth self-control, and delinquency four years later. Consistent with the conceptual model, marital conflict and youth self-control are directly related to delinquent behavior, and parenting is linked with delinquency through its relationship with youth self-control. Males are at a greater risk of delinquency compared with females, a relationship that is explained by lower levels of self-control. Contrary to the hypothesized model, parenting practices and youth self-control do not mediate the relationship between marital conflict and delinquent behavior, and parenting practices and male gender have no direct relationship with delinquency. Implications for social work practice are discussed.