Linear latent structure analysis: Mixture distribution models with linear constraints

A new method for analyzing high-dimensional categorical data, Linear Latent Structure (LLS) analysis, is presented. LLS models belong to the family of latent structure models, which are mixture distribution models constrained to satisfy the local independence assumption. LLS analysis explicitly considers a family of mixed distributions as a linear space, and LLS models are obtained by imposing linear constraints on the mixing distribution.LLS models are identifiable under modest conditions and are consistently estimable. A remarkable feature of LLS analysis is the existence of a high-performance numerical algorithm, which reduces parameter estimation to a sequence of linear algebra problems. Simulation experiments with a prototype of the algorithm demonstrated a good quality of restoration of model parameters.     

Reducing Risk on Machinery: A Field Evaluation Pilot Study of Risk Assessment

A pilot evaluation of the ANSI B11-TR3 Machinery Risk Assessment/Risk Reduction (RA/RR) Guideline was conducted. The TR3 guideline was introduced into five companies on one machinery system in each company with a second machine system serving as a control. A pre-post investigation was performed with safety conditions measured pre and post in both treatment and control and with risk reduction score measured only in the treatment machine system. NIOSH provided a commercially available risk assessment software to facilitate the process. Evaluation measures included avoided injuries, reduced exposure to machinery hazards, pretest and posttest knowledge demonstration, assessment of group processes following training, correct implementation of the guidelines, and degree to which risk reduction recommendations were implemented. The qualitative results of this pilot effort appear to be the best indicators for the way ahead in industrial machine risk assessment. All companies indicated that they derived value in participating in this study and in conducting risk assessments. Quantitative study results suggest that: (1) as measured by the knowledge of the participants before and after the TR3 training, the guidelines can be effective at enhancing employee knowledge of safe machine operations and (2) although the injury reduction trends appear successful, the small sample size in the study size should be considered in interpreting these early results.     

Economic Pressure, Maternal Depression, and Child Adjustment in Latino Families: An Exploratory Study

The goal of this study was to investigate the impact of poverty and economic pressure upon the adjustment of mothers and children in immigrant Latino families. Participants included 56 first generation Latina mothers who completed questionnaires addressing economic difficulties, depression, social support, and behavior problems exhibited by their children (30 boys, 26 girls) who ranged in ages from 4 to 13. Results indicate that maternal depression mediates the relationship between maternal economic pressure and child adjustment. Social support was found to further moderate the relationship between maternal depression and child internalizing problems. Gender differences indicated that relations were stronger among mothers of boys than mothers of girls.     

The Social Construction of Risk in a Rural Community: Responses of Local Residents to the 1990 Hagersville (Ontario) Tire Fire

This paper presents the findings of research relating to the 1990 Hagersville (Ontario) tire fire. After reviewing the literature on risk and risk perception, it begins by describing the event as well as the community in which it occurred. The reasons for adopting a qualitative research design are then established practical, conceptual, and methodological. The residents' accounts of the fire, evacuation, and aftermath in terms of concerns, anxieties, and responses are described. Five themes emerge: economic, community, health, environmental, and governance. The paper concludes by putting forward a case study-derived model of risk appraisal and management, and by relating the findings to policy issues.