Uniqueness of estimation and identifiability in mixture models

Further properties of the nonparametric maximum-likelihood estimator of a mixing distribution are obtained by exploiting the properties of totally positive kernels. Sufficient conditions for uniqueness of the estimator are given. This result is more general, and the proof is substantially simpler, than given previously. When the component density has support on N points, it is shown that all identifiable mixing distributions have support on no more than N/2 points. Identifiable mixtures are shown to lie on the boundary of the mixture model space. The maximum-likelihood estimate is shown to be unique if the vector of observations lies outside this space.     

How are companies planning now?—a survey

This article reports on the changes that have taken place in the long-range planning practices of several U.S. and Canadian firms over the last 5 years. In October 1974, the long-range practices of approximately 400 firms were reported in Long Range Planning. A follow-up survey of these same firms was recently completed. The percentage of responding companies that prepare some type of written long-range plan has not changed; however, there have been some changes in the extent and content of these plans. The mix of objectives, use of external factors, plans for growth, and methods for controlling the plan have all changed slightly between 1974 and 1979.     

An examination of common coping strategies used to combat driver fatigue

Driver fatigue is recognized as an important highway safety risk. Many organizations have published recommendations for coping with driver fatigue. The authors explored the effectiveness of 10 common coping strategies, using a case-controlled design to examine the use of coping strategies among a random sample of college students (N = 301). The students were questioned about their use of coping strategies for driver fatigue and their record of having experienced a dozing-related incident. Odds ratios were calculated and 4 strategies--taking a walk, drinking caffeinated beverages, stopping for a nap, and chewing ice--were found to predict an incident. Three other strategies, snacking, rolling the window down, and talking with a passenger, were found to be protective.     

Mapping the journey: outcome‐focused practice and the role of interim outcomes in family support services

Longitudinal costly evaluations will always be important in order to understand the factors that impact on child, family and community well‐being over the long and medium term. However, in a policy era that accords major importance to the achievement of outcomes, e.g. payment by results, ‘outcome theology’ can pose threats to service access and professional morale in family support. It is essential therefore, to ascertain the short‐term outcomes of services in order to capture the trajectory of progress by families under stress. This paper critiques the concept of ‘the outcome’. It traces the development of this trend in policy and describes an alternative but complementary approach, which is based on capturing interim outcomes in family support services.     

Inter‐agency Cooperation and New Approaches to Employability

This article examines the role of inter‐agency cooperation, which is one form of ‘partnership’, in new approaches to employability in the UK. The article articulates a ‘model for effective partnership working’ on employability. This model is applied first in a general review of employability policy and then to discuss case study research on the recent ‘Pathways to Work’ and ‘Working Neighbourhoods’ pilots. It is argued that successful partnerships need a clear strategic focus based on a necessity for inter‐agency cooperation and institutional arrangements that allow for shared ownership, trust and mutualism, and flexibility in resource‐sharing. While some of these factors are apparent in UK employability services, an over‐reliance on contractualism and centralized organizational structures may undermine partnership‐based approaches. Many of the success factors associated with effective partnership working appeared to be in place, even though the role of the Public Employment Service was fundamentally different in each case (as a key actor in implementing the first pilot, but largely withdrawing from the implementation role in the second). The article concludes by outlining the relevance of this model and the case study findings to discussions of the future development of employability policies and related partnership working.     

A systematic analysis of college substance use policies

College substance use policies provide guidelines for student behavior and influence campus culture. Although they are the primary environmental strategy to address campus substance use, policies have not been systematically compared and studied. We constructed a systematic review method to examine the accessibility, comprehensiveness, enforcement procedures, and clarity of college substance use policies. We developed an objective evaluation scheme for each of these 4 dimensions and then applied it to documented substance use policies from a sample of colleges and universities (N = 24). Policies were found to vary considerably but tended to specify compliance with local laws and emphasize student health and well-being. The next stage of campus policy review should examine actual implementation, evaluate potential differentiating factors among institutions, and assess the influence of policy on campus climate and student outcomes.     

Social Control and Intersectionality: A Multilevel Analysis of School Misconduct,Location, Race,Ethnicity, and Sex

Adolescent violence and misconduct, especially within schools, is a top sociological and educational concern because of the detrimental effects on adolescent physical health, emotional well-being, and educational progress. Concurrently, public schools in the United States are in the midst of a demographic transformation. More importantly, prior research suggests contextual characteristics are associated with rates of deviant behavior particularly in urban areas where racial and ethnic minorities reside. What remains uncertain, however, is the relationship between social control, intersectionality, and school misconduct. This study utilizes data from the Education Longitudinal Study of 2002 and incorporates multilevel modeling techniques to examine how the link between social control and adolescent school misconduct may differ by race, ethnicity, and biological sex in urban, rural, and suburban locations. The results suggest intersectionality may matter when understanding the associations between social control and school misconduct. The implications of how intersectionality may matter in social control are discussed.