On the unbiasedness of iterated gls estimators

We Formulate sufficienct conditions for the existonce of the expectation of iterated generalized expectation of the iterated generalized least squares estimator, which consequently guarantee its unbiasedness, The analysis is applied to the maximum likelihood estimator in the general linear model with normal disturbances, where a set of assumptions ensures convergence of the iteration as well as unbiasedness.     

Satisfaction with Life Scale in Adolescents: Evaluation of Factor Structure and Gender Invariance in a Norwegian Sample

Social Indicators Research - In spite of the significance of life satisfaction (LS) for adolescent health and well-being, the past decades have yielded limited progress in investigating the...     

Are Subsidiaries More Prone to Pollute? New Evidence from the EPA's Toxics Release Inventory*

Objective. Some scholars fear that because firms are no longer liable for the hazardous activities of their subsidiaries, the latter are under less corporate pressure to limit their pollution. However, researchers have yet to examine the environmental performance of subsidiaries. This reflects a more general failure on their part to test the effects different organizations have on pollution. Methods. To begin to remedy this situation, we use data from the EPA's Toxics Release Inventory to determine whether subsidiaries emit pollutants at a higher rate than other facilities in the chemical industry. Results. We find that subsidiaries have significantly higher emission rates than other facilities after controlling for several relevant factors. Conclusions. Results suggest how recent research on the structural determinants of environmental degradation might be advanced by focusing on the effects of specific organizational forms.     

Validity in an evaluation of Healthy Families Florida—A program to prevent child abuse and neglect

Evidence-based continuums have become a guide for identifying the level of evidence in evaluations of home visiting programs conducted to determine their effectiveness in preventing child abuse and neglect. While randomized controlled trials are required for the highest levels of evidence, quasi-experimental designs have also been specified as an appropriate alternative. Using a quasi-experimental evaluation of a home visiting program to prevent child abuse and neglect that adheres to the Healthy Families America model, this paper describes and illustrates how types of validity can be improved. More specifically, we address how threats to internal validity can be identified and reduced through statistical techniques; how construct validity may be strengthened using state records to measure the outcomes; and how external validity is affected by including or excluding study participants. After applying a variety of statistical adjustments to reduce selection bias, we found that the outcomes favored the home visiting program and increased after accounting for covariates that contributed to child abuse and neglect. This was true across the statistical techniques (traditional covariate and propensity score adjustment) used. For evaluations using quasi-experimental designs, recommendations relevant to the illustrations in the paper are also presented.     

The Influence of Graphical and Symbolic Language Manipulations on Responses to Self-Administered Questions

This article reports results from 14 experimental comparisonsdesigned to test 7 hypotheses about the effects of two typesof nonverbal languages (symbols and graphics) on responses toself-administered questionnaires. The experiments were includedin a survey of 1,042 university students. Significant differenceswere observed for most comparisons, providing support for allseven hypotheses. These results support the view that respondents’answers to questions in self-administered surveys are influencedby more than words. Thus, the visual presentation of questionsmust be taken into consideration when designing such surveysand, especially, when comparing results across surveys in whichthe visual presentation of questions is varied.     

An Auction Model of Canadian Temporary Immigration for the 21st Century

Temporary Canadian immigration has grown beyond traditional programs for students, caregivers and agricultural workers to include trade-related temporary visas under NAFTA and the GATS. Current Canadian debates envision supplanting Canada's permanent immigration programme with a temporary visa programme to remove skill shortages. Several questions emerge under these temporary schemes including who should choose the number of temporary immigrants and under what employment conditions. This paper offers an alternative policy to the current government-determined quota on temporary visas to answer these two questions. Under the proposed scheme offered in this paper, a Canadian worker can place a job voucher up for auction on the Internet. If the Canadian worker finds an acceptable offer for his one-year (or less) voucher, then the temporary immigrant is permitted to seek a job in Canada. Thus, under this auction scheme Canadian workers are compensated for the presence of temporary immigrants, and the actual number of temporary immigrants admitted depends on the total number of Canadian workers who sell their vouchers, not on a government fat.     

Negotiated Project Engagements: Learning from Experience

How far is it possible to capture the lessons tobe drawn from successive projects that involveintervention by social scientists within or betweenorganizations, whether acting as researchers, asconsultants, as agents of change, or in some combination ofthese roles? This paper outlines the way in which aframework was developed, by staff and associates of TheTavistock Institute, for examining the varied and often subtle influences of successive“negotiated project engagements” on thedevelopment of wider personal, institutional, anddisciplinary programs. This framework is designed totake into account the contrasting perspectives of the investigatorsthemselves, of their organizational hosts, and of anyexternal sponsors whose primary concern will normally bewith project outcomes at a more generalized level. As an illustration, particular reference ismade to the experience of a pioneering project concernedwith policy-making in city government. This project wasundertaken to advance the understanding and practice of public planning, while also exploring thepotential for synergy between the perspectives ofoperational research and applied social science. Thepaper concludes with some speculations about thepotential for further developing this kind of frameworkin supporting experiential learning.     

A Dynamic Model to Assess Microbial Health Risks Associated with Beneficial Uses of Biosolids

There is increasing interest in the development of a microbial risk assessment methodology for regulatory and operational decision making. This document presents a methodology for assessing risks to human health from pathogen exposure using a population-based model that explicitly accounts for properties unique to an infectious disease process, specifically secondary transmission and immunity. To demonstrate the applicability of this risk-based method, numerical simulations were carried out for a case study example in which the route of exposure was direct consumption of biosolids-amended soil and the pathogen present in the soil was enterovirus. The output from the case study yielded a decision tree that differentiates between conditions in which the relative risk from biosolids exposure is high and those conditions in which the relative risk from biosolids is low. This decision tree illustrates the interaction among the important factors in quantifying risk. For the case study example, these factors include biosolids treatment processes, the pathogen shedding rate of infectious individuals, secondary transmission, and immunity. Further refinement in methods for determining biosolids exposures under field conditions would certainly increase the utility of these approaches.