Development of r,T hybrid sampling plans for exponential lifetime distributions

SUMMARY In the original hybrid reliability acceptance sampling plan RASP developed by Epstein for the exponential lifetime distribution, the sample size n and the number of failures r to be observed are determined given the truncation time T . However, these plans cannot be used when test items are expensive and or limited in number. Therefore, one wishes to have a plan in which n is given. In this paper, we develop hybrid RASPs in which r and T are determined, given n. These plans are tabulated for various combinations of parameter values, so that one may easily determine an appropriate plan.     

To market, to market: the changing face of grocery retailing

Over the past few years, grocery retailing has undergone a tremendous transformation which was driven mainly by changing consumer characteristics. In order to accommodate these changes, the industry has responded in three ways. The most important of these is the introduction of new technology, particularly efficient consumer response (ECR). The second change has to do with innovations in product and/or service offerings. The final transformation is the organisational restructuring and the increasing number of mergers and acquisitions in the industry at both the manufacturer and retailer levels. The implications of these transformations on the marketing mix, productivity and manufacturer-retailer relationships are discussed.     

Privatization, provision, and targeting: Trends and policy implications for social security in the United States

This paper examines several important trends in the changing structure of social security in the United States and their impact on the elderly in different income groups. These trends involve the shifting public/private mix of retirement income, the declining replacement rates of public benefits, and reforms for targeting benefits by age. An analysis of these trends suggests that (a) social security will provide declining economic support for those most in need; (b) middle- and upper-income groups will have a diminished stake in social security, reducing the programme's political base of support; (c) increasing reliance on occupational pensions will heighten the need for greater public regulation of private schemes; (d) an unplanned two-tiered system of pensions will emerge, with the first tier consisting of a whittled-down version of social security to provide a predominant source of retirement income for low-income wage earners and the second tier consisting of private pensions for middle- and upper-income groups.     

Inventory Sharing in the Presence of Commodity Markets

This study investigates the value of inventory sharing in the presence of spot and forward markets. We consider a multi‐period setting where two firms process a common commodity to meet stochastic demands. They can buy and sell the commodity through both the spot and forward markets. They can also share the commodity if one has leftover inventory while the other has excess demand. We first characterize the equilibrium strategies of the two firms. Our analysis reveals that in such a context, the value of inventory sharing is low when the forward price is directly used to value the sharing transactions. We then develop a structured trans‐shipment price scheme that uses a linear combination of the spot and forward prices. We show that this method can substantially increase the value of inventory sharing. Our analysis also reveals that in the presence of liquid spot and forward markets, the value of inventory sharing mainly results from the difference of the transaction costs, and it increases if the market in which firms operate becomes more competitive.     

Graphical evaluation of robust parameter designs based on extended scaled prediction variance and extended spherical average prediction variance

For any response surface design, there are locations in the design region where responses are estimated well and locations where estimation is relatively poor. Consequently, graphical evaluation—such as variance dispersion graphs and the fraction of design space—is used as an alternative to a single-valued criterion. Such plots are used to investigate and compare the prediction capabilities of certain response surface designs currently available to the researcher. In this article, we propose the extended scaled prediction variance and extended spherical average prediction variance as prediction methods. We also illustrate how graphical methods can be employed to evaluate robust parameter designs.     

Analysis of inaccurate data with mixture measurement error models

Measurement error, the difference between a measured (observed) value of quantity and its true value, is perceived as a possible source of estimation bias in many surveys. To correct for such bias, a validation sample can be used in addition to the original sample for adjustment of measurement error. Depending on the type of validation sample, we can either use the internal calibration approach or the external calibration approach. Motivated by Korean Longitudinal Study of Aging (KLoSA), we propose a novel application of fractional imputation to correct for measurement error in the analysis of survey data. The proposed method is to create imputed values of the unobserved true variables, which are mis-measured in the main study, by using validation subsample. Furthermore, the proposed method can be directly applicable when the measurement error model is a mixture distribution. Variance estimation using Taylor linearization is developed. Results from a limited simulation study are also presented.     

Longitudinal trajectories of maternal parenting stress in Korean families: Children's executive function and school adjustment

A majority of mothers experience parenting stress in daily life; however high levels of maternal stress have been recognized as a risk factor for children's developmental outcomes. We examined trajectories of maternal parenting stress across childhood, and their longitudinal relations to children's executive function and school adjustment. Data were drawn from the Panel Study on Korean Children (PSKC), which included 1754 mothers across five waves measured at children ages 3, 4, 5, 6, and 7 (boys = 51%). Results of Latent Growth Curve Modeling (LGCM) revealed that, on average, maternal parenting stress decreased over time, but there were significant variabilities in the initial levels at age 3 and changes across early through middle childhood. High initial levels of stress and an increase in maternal parenting stress over time were associated with lower executive function at age 7 in planning-organizing and attention concentration. An increment in maternal parenting stress over time was related to poorer school adjustment at age 7, measured by classroom behavior, positive approach to learning, and child-peer and child-teacher relationships. These findings support cultural commonality and may contribute to the instantiation of culturally universal, early preventions and interventions to support mothers’ mental health. Efforts aimed at reducing maternal parenting stress early in development may promote better long-term developmental outcomes, including executive functioning and school adjustment of children in their first year of elementary school.     

Intimate partner violence and preschool self-regulation: Examining the role of maternal emotion socialization in Black families

The ways that parents respond to children's negative emotions shape the development of self-regulation across early childhood. The objective of this study was to examine child self-regulation in the context of intimate partner violence (IPV) exposure in a sample of Black, economically marginalized mothers and their young children (aged 3–5 years, N = 99). The study investigates the conditional effects of emotion socialization practices that (1) encourage expression of and problem-solving around negative affect (“supportive”), and (2) encourage suppression of affective displays (“suppressive”) on children's self-regulation. We found a significant association between higher child self-regulation and supportive parental reactions in the context of psychological IPV. We also found a significant association between higher child self-regulation and suppressive parental reactions in the context of psychological IPV. Our findings are consistent with prior research suggesting Black parents who teach varied strategies for emotional expression may promote children's adaptation in high-stress family environments. Macrosystem factors such as systemic racism and discrimination as well as the threat of family violence may shape how parents approach emotion socialization and the teaching of affective self-expression and self-regulation.