Robust mixture regression modeling using the least trimmed squares (LTS)-estimation method

Mixture regression models are used to investigate the relationship between variables that come from unknown latent groups and to model heterogenous datasets. In general, the error terms are assumed to be normal in the mixture regression model. However, the estimators under normality assumption are sensitive to the outliers. In this article, we introduce a robust mixture regression procedure based on the LTS-estimation method to combat with the outliers in the data. We give a simulation study and a real data example to illustrate the performance of the proposed estimators over the counterparts in terms of dealing with outliers.     

Identifying and Explaining Different Poverty Trajectories Using a Group‐based Trajectory Analysis – A Case Study of South Korea

In this study, we propose a group‐based trajectory analysis to examine why and how people fall into and out of poverty despite spiralling public expenditure on anti‐poverty policies. By analyzing the poverty experiences of 1,001 low‐income households between 1999 and 2008 in Korea, we identify five groups based on their poverty trajectories: exiting, declining, slowly rising, rapidly rising and chronic. Household members in each group demonstrate heterogeneous labour market experiences, educational levels and demographic factors. The exiting group has a high proportion of full‐time workers, high school graduates, and younger and male‐headed households, whereas the chronic group has more part‐time workers, high school dropouts, and older and female‐headed households. Among the declining, slowly rising and rapidly rising groups, educational background, age and sex are factors that differentiate the poverty dynamics of household members. Lastly, a number of social policies for helping low‐income households to leave and stay out of poverty are proposed.     

Parameter estimation for mixtures of skew Laplace normal distributions and application in mixture regression modeling

In this article, we propose mixtures of skew Laplace normal (SLN) distributions to model both skewness and heavy-tailedness in the neous data set as an alternative to mixtures of skew Student-t-normal (STN) distributions. We give the expectation–maximization (EM) algorithm to obtain the maximum likelihood (ML) estimators for the parameters of interest. We also analyze the mixture regression model based on the SLN distribution and provide the ML estimators of the parameters using the EM algorithm. The performance of the proposed mixture model is illustrated by a simulation study and two real data examples.     

Could “Acculturation” Effects Be Explained by Latent Health Disadvantages Among Mexican Immigrants?

This paper tests portions of a new theory of immigrant health by focusing exclusively on latent biomarkers of future health risks. Using data from the National Health and Nutrition Examination Survey III, 1988–1994 – we uncover the typically observed immigrant health advantage among recent immigrants that diminishes among long‐term immigrants. In addition, we observe worse health among U.S.‐born Mexican Americans relative to non‐Hispanic Whites. Finally, although our theory suggests that recent immigrants may have latent health risks due to disadvantaged childhood experiences, we do not find evidence in support of this theory.     

The stability of exchange networks

Economic and sociological exchange theories predict divisions of exchange benefits given an assumed fixed network of exchange relations. Since network structure has been found to have a large impact on actors’ payoffs, actors have strong incentives for network change. We answer the question what happens to both the network structure and actor payoffs when myopic actors change their links in order to maximize their payoffs. We investigate the networks that are stable, the networks that are efficient or egalitarian with varying tie costs, and the occurrence of social dilemmas. Only few networks are stable over a wide range of tie costs, and all of them can be divided into two types: efficient networks consisting of only dyads and at most one isolate, and Pareto efficient and egalitarian cycles with an odd number of actors. Social dilemmas are observed in even-sized networks at low tie costs.     

The Effect of Adult Children’s Working Hours on Visits to Elderly Parents: A Natural Experiment in Korea

Population Research and Policy Review - Despite its significant policy implications, little is known about the impact working hours have on how often workers visit their elderly parents. Evidence...     

Static-dynamic uncertainty strategy for a single-item stochastic inventory control problem

We consider a single-stage inventory system facing non-stationary stochastic demand of the customers in a finite planning horizon. Motivated by the practice, the replenishment times need to be determined and frozen once and for all at the beginning of the horizon while decisions on the exact replenishment quantities can be deferred until the replenishment time. This operating scheme is refereed to as a “static-dynamic uncertainty” strategy in the literature [3]. We consider dynamic fixed-ordering and linear end-of-period holding costs, as well as dynamic penalty costs, or service levels. We prove that the optimal ordering policy is a base stock policy for both penalty cost and service level constrained models. Since an exponential exhaustive search based on dynamic programming yields the optimal ordering periods and the associated base stock levels, it is not possible to compute the optimal policy parameters for longer planning horizons. Thus, we develop two heuristics. Numerical experiments show that both heuristics perform well in terms of solution quality and scale-up efficiently; hence, any practically relevant large instance can be solved in reasonable time. Finally, we discuss how our results and heuristics can be extended to handle capacity limitations and minimum order quantity considerations.     

Assessing Racial and Ethnic Differences in Attitudes towards the Use of Physical Discipline in Parenting: A Mixed-Methods Approach

Using a concurrent nested mixed-methods approach, this study assessed racial and ethnic differences in attitudes towards the use of physical discipline in parenting based on data recently collected in Nebraska. Relative to Non-Hispanic White parents, African American parents were more likely to approve the practice of physical punishment to correct misbehavior of children, whereas Hispanic parents were less likely to support physical punishment. There was a positive relationship between acculturation and approval of physical discipline among Hispanic parents. Understanding these differences can help inform the design and implementation of future parenting education programs for parents of different racial and ethnic backgrounds.     

Carabid beetles in green infrastructures: the importance of management practices for improving the biodiversity in a metropolitan city

Green infrastructure in urbanized areas has a dual purpose that achieves both sociological and ecological goals. To benefit society and the urban ecosystem, green infrastructure should be effectively managed. We investigated carabid diversity and assemblage structure as indicators of biodiversity in green infrastructures in a rapidly developing urban area to identify the habitat’s values. In addition, we attempted to reveal the effect of environmental variables (e.g., vegetation structure, soil, and disturbance) that strongly contribute to carabid diversity and assemblage structure. Of the collected organisms, 6,154 individuals representing 20 carabid species were identified in the green infrastructure. Those species with flight ability and that were found in dry habitats were widely distributed and dominated green infrastructures. Carabid assemblages changed significantly in response to management practices. These changes were both positive and negative, with the negative changes increasing the instability of the carabid assemblages through the destruction of their habitat. Other factors, such as the presence of original habitat, habitat age, and habitat succession, also had a considerable effect on carabid diversity. We revealed that management practices prevented habitat succession, and these interactive effects determined carabid diversity and structure in green infrastructures.     

Disparities in Human Papillomavirus Vaccine Literacy and Vaccine Completion Among Asian American Pacific Islander Undergraduates: Implications for Cancer Health Equity

Abstract

Purpose: Low rates of human papillomavirus (HPV) vaccination among young Asian American and Pacific Islander (AAPI) women need to be addressed, particularly given the high incidence of cervical cancer in this population. The current study aims to investigate predictors of HPV vaccination in young AAPI and non-Latina white (NLW) women. Methods: A secondary data analysis was conducted of a health survey administered to college-aged women (N = 2,270) at a large public university in the Midwest. Andersen's behavioral model of health services utilization guided the study theoretically, and hierarchical logistic regression analysis was conducted to investigate research aim. Results: NLW women had a significantly higher rate of vaccine completion than AAPI women (NLW = 60.7%; AAPI = 38.6%). NLW women also scored higher on all 5 measures of HPV vaccine literacy than AAPI women. Both groups of undergraduate women reported that increasing age, knowledge about HPV, greater use of gynecological services, and knowing someone who had cancer were significant factors related to HPV vaccination completion. In the NLW group, father's income was also found to be a predictor of HPV vaccination completion. Conclusions: Rate and predictors of HPV vaccination completion vary between NLW and AAPI women. Greater promotion of HPV literacy and gynecological service use should be made to young AAPI women to increase their HPV uptake. Further research should examine sociocultural factors that could hinder or promote HPV vaccination in young AAPI women.