Comparison of Operating Characteristics of Commonly Used Sample Size Re-Estimation Procedures in a Two-Stage Design

In group sequential clinical trials, there are several sample size re-estimation methods proposed in the literature that allow for change of sample size at the interim analysis. Most of these methods are based on either the conditional error function or the interim effect size. Our simulation studies compared the operating characteristics of three commonly used sample size re-estimation methods, Chen et al. (2004), Cui et al. (1999), and Muller and Schafer (2001). Gao et al. (2008) extended the CDL method and provided an analytical expression of lower and upper threshold of conditional power where the type I error is preserved. Recently, Mehta and Pocock (2010) extensively discussed that the real benefit of the adaptive approach is to invest the sample size resources in stages and increasing the sample size only if the interim results are in the so called “promising zone” which they define in their article. We incorporated this concept in our simulations while comparing the three methods. To test the robustness of these methods, we explored the impact of incorrect variance assumption on the operating characteristics. We found that the operating characteristics of the three methods are very comparable. In addition, the concept of promising zone, as suggested by MP, gives the desired power and smaller average sample size, and thus increases the efficiency of the trial design.     

A note on scheffé's method of deriving confidence sets for directions and ratios of normals

Scheffé (1970) introduced a method for deriving confidence sets for directions and ratios of normals. The procedure requires use of an approximation and Scheffé provided evidence that the method performs well for cases in which the variances of the random deviates are known. This paper extends Scheffé's numerical integrations to the case of unknown variances. Our results indicate that Scheffé's method works well when variances are unknown     

Child Maltreatment Intervention: Directions and Issues

This article begins with a brief review of various non-medical intervention procedures for child maltreatment. Psychological intervention is reviewed in more depth, with an emphasis placed on those treatments which have been empirically evaluated. Finally, the article discusses methodological and ethical issues concerning outcome research on maltreatment intervention.     

Assent-maximizing social choice

We take a decision theoretic approach to the classic social choice problem, using data on the frequency of choice problems to compute social choice functions. We define a family of social choice rules that depend on the population’s preferences and on the probability distribution over the sets of feasible alternatives that the society will face. Our methods generalize the well-known Kemeny Rule. In the Kemeny Rule, it is known a priori that the subset of feasible alternatives will be a pair. We define a distinct social choice function for each distribution over the feasible subsets. Our rules can be interpreted as distance minimization—selecting the order closest to the population’s preferences, using a metric on the orders that reflects the distribution over the possible feasible sets. The distance is the probability that two orders will disagree about the optimal choice from a randomly selected available set. We provide an algorithmic method to compute these metrics in the case where the probability of a given feasible set is a function only of its cardinality.     

General symbolic definitions and subjective well‐being

In recent years evidence has suggested that demographic factors such as income and status have only a modest relationship to subjective well‐being. As a result, much attention has been paid to internal rather than external factors. Discrepancy perceptions approaches, particularly multiple discrepancy theory, link internal subjective factors with external conditions in explaining subjective well‐being. This study suggests that discrepancy perceptions are only one way people differ in defining reality, and that symbolic interaction theory provides a broader and better framework with which to examine subjective well‐being. Specifically, using the General Social Survey, this study tests whether differing general symbolic definitions have an independent influence on subjective well‐being. Results indicate that general symbolic definitions influence subjective well‐being, and this influence does not depend on their conditioning discrepancy perceptions or demographic life conditions.     

Long-Term Trends In Migratory Behavior In A Developing Country: The Case of Mexico

Comparable lifetime migration relationships are estimated for Mexico for 1950, 1960, and 1970. Moreover, migration flows from each state to every other state are separately examined for each year. A number of significant changes over time are evident in the responsiveness of Mexican internal migrants to various socioeconomic stimuli, and appreciable differences are also evident across space. Moreover, a threshold is observed such that up to about 340 miles higher origin earnings deter migration, but beyond this distance higher earnings actually encourage migration.     

Young African American Males: Barriers to Access to Health Care

African American males continue to experience an unacceptable and disproportionate number of health disparities when compared with other racial and ethnic groups. Young African American males can expect to live the least amount of time when compared to any other ethnic minority or racial sub-group. Understanding the obstacles and barriers that impede access to health care and wellness services among young African American males is essential to begin the process of decreasing health disparities. The goal of this qualitative study was to explore and identify the barriers experienced by young African American males in accessing health care services while also creating a rare opportunity to give voice to young African American males. The study results indicate that young African American males have multiple perceptions of barriers to health care services. Their perceptions fell into three categories: the negative impact of environment or community, lack of finances or no insurance, and distrust of medical practices associated with race history resulting in accessing healthcare as a last resort. Additional research is needed to craft community-based programs to: a) educate young African American males on the importance of preventative strategies to maintain wellness; and b) ensure that the appropriate medical and wellness services are available and reaching young African American males in need.     

Globalizing history and historicizing globalization

In arguing for the twin projects of globalizing history and historicizing globalization, this paper locates the development of historical scholarship in its own historical context. For the most part, professional historical scholarship has focused on the experiences of national communities and has taken European modernity as the principal guide to the understanding of the world's various societies. In the interests of enhancing understanding of the world and its development through time, there is a clear need to globalize history and historicize globalization. From ancient to contemporary times, several distinct interests—notably those of empire, business and mission—have driven or at least informed efforts to understand the larger world. Since World War II, the production of knowledge about the larger world has come largely through area studies scholarship, which itself has clearly reflected the interests of contemporary states. While area studies projects have experienced remarkable success in developing reliable information and constructing meaningful knowledge about the larger world, it has become clear that scholarship focusing exclusively on individual states or local communities is inadequate for purposes of understanding large-scale globalizing processes that have touched many peoples and influenced the development of individual societies, as well as the world as a whole. Following up on this recognition, recent scholarship in world history suggests that globalization has a very long history indeed. In combination, the projects to globalize history and historicize globalization promise to yield an enriched understanding of the world and its development through time.     

Public policy and the socioeconomic mortality differential in infancy

This paper discusses some of the findings and policy implications of a recently completed study of socioeconomic differences in infant mortality in eight metropolitan areas of Ohio at three points in time. The study revealed that, in spite of a considerable decline in the overall rate of infant mortality since 1960, the inverse socioeconomic differential remains as wide as ever. This clearly suggests that, although maternal and child health has improved overall, the lower economic groups in our society still do not have equal access either to health care or to other amenities essential to the maintenance of good health. Moreover, consideration of recent and current policy proposals with respect to welfare programs in general, and maternal and child health care programs in particular, leads to the conclusion that this situation is not likely to change in the near future. Finally, some policy recommendations for enhancing the health status of low-income families are offered.The research on which this paper is based has been supported by the Maternal and Child Health and Crippled Children's Services Research Grants Program (Grant MCJ-390520-01); Bureau of Community Health Services, HSA, PHS, DHHS.