The spokane heart study: weibull regression and coronary artery disease

Coronary artery calcium is a marker of coronary artery disease and measures the progression of atherosclerosis. It is measured by electron beam computed tomography, and the measured amount of coronary artery calcium is highly skewed to the right and left censored. The distribution of coronary artery calcium appears to be Weibull. We propose a Weibull regression model and we analyze the data using these techniques. Our analysis is based on data from the Spokane Heart Study, which is a cohort of about a thousand subjects that are assessed every two years for coronary artery calcium and risk factors of coronary artery disease. The major focus of the heart study is to determine the natural history of atherosclerosis in its early phase, and we analyze the data as a cross-sectional study with 859 subjects. We would also like to highlight the use of Weibull regression techniques in situations like this, where we have extreme right skewed data. Our main emphasis will be on examining the effect of the traditional risk factors of age, gender, lipid profile (cholesterol and HDL), patient history of lipid abnormality, hypertension, and smoking, and other family history risks on coronary artery calcium. We found that the most important factors influencing the disease were age, sex, and patient history of smoking and lipid abnormality.     

An approximation to the poly-t distribution

This investigation examines an approximation to the poly-t distribution, which often occurs in the Bayesian analysis of a linear model. The approximation allows one to compute the mean vector and dispersion matrix of any k/0 multivariate poly-t distribution in such a way that only univariate and bivariate numerical integrations are required. A numerical study depicts the advantages and disadvantages of the approximation.     

Structural changes in multivariate regression models

This study generalizes the work of chin choy and Broemeling (1980) who investigated the change in the regression parameters of univariate linear models.

The marginal posterior distributions of the change point, the regression matrices,and the precision matrix are found with the use of a proper multivariate normal-Wishart distribution for the parameters of the model.

A numerical study is undertaken in order to gain some insight into the effect that changes in sample size and certain parameter values have on these marginal posterior distributions.     

A proposal for a new screening paradigm and tool called Exercise Assessment and Screening for You (EASY)

The Exercise Assessment and Screening for You (EASY) is a tool developed to help older individuals, their health care providers, and exercise professionals identify different types of exercise and physical activity regimens that can be tailored to meet the existing health conditions, illnesses, or disabilities of older adults. The EASY tool includes 6 screening questions that were developed based on an expert roundtable and follow-up panel activities. The philosophy behind the EASY is that screening should be a dynamic process in which participants learn to appreciate the importance of engaging in regular exercise, attending to health changes, recognizing a full range of signs and symptoms that might indicate potentially harmful events, and becoming familiar with simple safety tips for initiating and progressively increasing physical activity patterns. Representing a paradigm shift from traditional screening approaches that focus on potential risks of exercising, this tool emphasizes the benefits of exercise and physical activity for all individuals.     

Looks can be deceiving: Using a risk assessment instrument to evaluate the out-comes of child protection services

This study explores the use of a risk assessment instrument based on the Illinois CANTS-17B in the child protection services division of a large urban public social services agency. It addresses the usefulness of the instrument as an outcome measure tool, that is, as means of measuring successful case outcomes based on reductions in maltreatment risk between case opening and case closing. Two separate studies were conducted in which the initial and closing risk levels on the 14-item scale were compared. Results were highly statistically significant in both studies, with the difference being in the expected and desired direction: a decrease in risk scores at case closing. However, a more detailed exploration of the data and of the practice issues involved in the agency setting strongly suggests that these differences are largely due to the artificial inflation of initial risk scores by caseworkers in order to ensure children's acceptance for ongoing child protection services. These factors are discussed in detail, along with the policy decisions that ensued from the study.     

A note on the annihilation number and 2-domination number of a tree

In 2014, Desormeaux et al. (Discrete Math 319:15–23, 2014) proved a relationship between the annihilation number and 2-domination number of a tree. In this note, we provide a family of bounds for the 2-domination number of a tree based on the amount of vertices of small degree. This family of bounds extends current bounds on the 2-domination number of a tree, and provides an alternative proof for the relationship between the annihilation number and the 2-domination number of a tree that was shown by Desormeaux et al.     

False Assumptions About the Determinants of Mexican-American and Negro Economic Absorption

It generally is believed that with age and time in the urban industrial community, differences between rural-reared and urban-reared persons decline or disappear. This longitudinal study of 973 families (280 Mexican-Americans, 280 Negroes, and 413 Anglos) in Racine, Wisconsin, finds little significant change (1960–1971) in the relative position of Mexican-Americans and Negroes on occupational level, income, and level of living, even though controls for age, education, urban work experience, time in the community, and other pertinent variables are introduced. These findings suggest that the community is organized in such a way as to facilitate better the economic absorption of its Anglo inmigrants than Negroes from the South or Mexican-Americans from Southwest, in spite of the fact that numerous programs were introduced in the United States during the 1960s, with the purpose of aiding the less fortunate in our society. Race/ethnicity remains the most powerful determinant of a family's position in the community.     

Relative acceptability: A proposed strategy for the bargaining game

Theory and Decision - In bargaining situations an actor faces a bifocal problem: He wants the best deal possible for himself, but unless his choice is coordinated with the antagonist's he is...