Testing for Additivity at Select Mixture Groups of Interest Based on Statistical Equivalence Testing Methods

Several assumptions, defined and undefined, are used in the toxicity assessment of chemical mixtures. In scientific practice mixture components in the low-dose region, particularly subthreshold doses, are often assumed to behave additively (i.e., zero interaction) based on heuristic arguments. This assumption has important implications in the practice of risk assessment, but has not been experimentally tested. We have developed methodology to test for additivity in the sense of Berenbaum (Advances in Cancer Research, 1981), based on the statistical equivalence testing literature where the null hypothesis of interaction is rejected for the alternative hypothesis of additivity when data support the claim. The implication of this approach is that conclusions of additivity are made with a false positive rate controlled by the experimenter. The claim of additivity is based on prespecified additivity margins, which are chosen using expert biological judgment such that small deviations from additivity, which are not considered to be biologically important, are not statistically significant. This approach is in contrast to the usual hypothesis-testing framework that assumes additivity in the null hypothesis and rejects when there is significant evidence of interaction. In this scenario, failure to reject may be due to lack of statistical power making the claim of additivity problematic. The proposed method is illustrated in a mixture of five organophosphorus pesticides that were experimentally evaluated alone and at relevant mixing ratios. Motor activity was assessed in adult male rats following acute exposure. Four low-dose mixture groups were evaluated. Evidence of additivity is found in three of the four low-dose mixture groups. The proposed method tests for additivity of the whole mixture and does not take into account subset interactions (e.g., synergistic, antagonistic) that may have occurred and cancelled each other out.     

THE EMERGENCE OF TRENDSETTERS FOR FASHIONS AND FADS:

Analyses of fads and fashions often note the importance of trendsetters whose early adoption of novelties provides an example for others to follow. However, trendsetting is usually taken for granted; there is no effort to explain why some groups assume fashion leadership. This article seeks to account for the rise of kogaru (stylish high-school girls) as trendsetters in 1990s Japan. We argue that trendsetting requires resources—particularly leisure time to devote to fashion, disposable income, and communication networks. Kogaru became trendsetters because they gained these resources at a time when the female college students who preceded them had less time for trendsetting, and when economic recession made inexpensive items of the sort kogaru could afford more desirable fashion objects. At the same time, new electronic technologies sped the flow of information among kogaru, while media coverage of this new social type gave kogaru visibility in the larger society.     

WHEN MEN ARE THE MINORITY: The Case of Men in Nursing

Based on in-depth interviews with a nonprobability sample of male nurses, this study argues that while male nurses do experience the interaction dynamics associated with tokenism as outlined by Kanter (1977a, 1977b), their experience is substantially different from that of female tokens because of socio-cultural factors that interact with group proportions in forming patterns of group interaction. Not only do male nurses react differently to the dynamics of visibility, polarization, and assimilation, but gender-related issues of status and stigma are also important to them. Although Kanter's framework is applicable to male nurses, many of the differences they experience compared to female tokens are attributable to socio-cultural definitions of masculinity and femininity as well as gender-based issues of status rather than group proportions alone. Thus, these findings suggest that socio-cultural factors, interacting with group proportions, strongly influence patterns of interaction among nurses.     

About the Authors

Sociological Forum -     

Examining outpatient health care utilization among adults with severe or profound intellectual disabilities living in an urban setting: a brief snap shot

The present study examined the health status and outpatient health care utilization among 52 adults with severe or profound intellectual disabilities (IDs) living with their families or in group homes in New York City. Bivariate and regression analyses among demographic variables, medical conditions, health care utilization, and type of living situation were conducted. Findings indicate that demographic factors and health statuses were similar regardless of living situation, except for age and the presence of Down Syndrome, that is, younger people and people with Down Syndrome were more likely to live with family than in group homes. The results indicated that regardless of where they lived, individuals had high rates (70%) of overweight/obesity. The mean number of internal medicine, specialty medicine, nursing, and total clinic visits were significantly higher for those living in group homes compared to those living with their families. The findings and their implications are discussed with respect to social work policy and practice.     

A spatial analysis of population dynamics and climate change in Africa: potential vulnerability hot spots emerge where precipitation declines and demographic pressures coincide

We present an integrative measure of exposure and sensitivity components of vulnerability to climatic and demographic change for the African continent in order to identify “hot spots” of high potential population vulnerability. Getis-Ord Gi* spatial clustering analyses reveal statistically significant locations of spatio-temporal precipitation decline coinciding with high population density and increase. Statistically significant areas are evident, particularly across central, southern, and eastern Africa. The highly populated Lake Victoria basin emerges as a particularly salient hot spot. People located in the regions highlighted in this analysis suffer exceptionally high exposure to negative climate change impacts (as populations increase on lands with decreasing rainfall). Results may help inform further hot spot mapping and related research on demographic vulnerabilities to climate change. Results may also inform more suitable geographical targeting of policy interventions across the continent.     

Performing the role of ethnographer: processing and managing the emotional dimensions of prison research

This article presents a reflective account of the emotional dimensions of in-depth field research in prisons. Drawing on the work of Goffman to make sense of ethnographic processes and techniques, it is argued that performance and impression management play crucial roles in the research process. However, it is suggested that there are commensurate emotional costs associated with the roles and identities that ethnographers might enact in the field. It is argued that the finer details of ethnographic practice can be better understood when the emotional dimensions of research experiences are carefully analysed and processed.     

Workers' Protest in Egypt: Neo-liberalism and Class Struggle in 21st Century

From 1998 to 2008 some 2 million Egyptian workers participated in 2,623 factory occupations, strikes, demonstrations, or other collective actions. This social movement does not have a national leadership or program and has not been supported by the Egyptian Trade Union Federation. It is propelled by locally generated grievances that have been produced by the acceleration of the neo-liberal transformation of Egypt since 2004. This workers movement has not changed the existing structures of power that constrain Egyptian working people because the informal, local networks that have sustained the movement are, by their nature, unable to organize a national-scale political movement on their own.