Solving problems in parameter redundancy using computer algebra

A model, involving a particular set of parameters, is said to be parameter redundant when the likelihood can be expressed in terms of a smaller set of parameters. In many important cases, the parameter redundancy of a model can be checked by evaluating the symbolic rank of a derivative matrix. We describe the main results, and show how to construct this matrix using the symbolic algebra package Maple. We apply the theory to examples from the mark-recapture field. General code is given which can be applied to other models.     

Understanding political pricing of labor services: The Davis-Bacon Act

Examples of divergence between the intended (stated) and actual consequences of government intervention in the marketplace abound. In this paper, two legislative attempts to specify wage rates on government contracts are analyzed. The Davis-Bacon Act has been successful in forcing government contractors to pay the prevailing union wage rate. In contrast, the Walsh-Healey Act has been ineffective in establishing minimum wage scales on most government contracts. Analysis indicates that the success of one and the failure of the other is due to differences in enforcement costs, special interest group support, the concentration of opposition, and the narrower scope of Davis-Bacon.     

Graphical Communication of Uncertain Quantities to Nontechnical People

Nine pictorial displays for communicating quantitative information about the value of an uncertain quantity, x , were evaluated for their ability to communicate , p ( x > a ) and p ( b > x > a ) to well-educated semi-and nontechnical subjects. Different displays performed best in different applications. Cumulative distribution functions alone can severely mislead some subjects in estimating the mean. A "rusty" knowledge of statistics did not improve performance, and even people with a good basic knowledge of statistics did not perform as well as one would like. Until further experiments are performed, the authors recommend the use of a cumulative distribution function plotted directly above a probability density function with the same horizontal scale, and with the location of the mean clearly marked on both curves.     

Exchange curves for fixing batch quantities

The problem considered is that of choosing batch quantities to minimize costs, subject to the constraints that neither overall set-up costs nor overall set-up time can be increased beyond certain limits. Theoretical and graphical solutions are obtained for two possible formulations of the problem, and a simple practical procedure is suggested.     

Lesbians Define Themselves: Diversity in Lesbian Identification

Ninety-nine self-identified lesbians provided definitions of what being a lesbian meant to them. A content analysis revealed two major categories: politically-based definitions and nonpolitical definitions. The political definitions included two highly interrelated subgroups, one of definitions based on woman-identification and the other including a broader world view that included affiliations with other oppressed groups. Nonpolitical definitions included four subgroups; those who defined lesbianism as sex/love with women, lesbianism as a true essence, just happening to love a woman, and lesbianism as only one small aspect of the person. There were only a few differences between women who cited political definitions and those with nonpolitical definitions. Lesbians who provided political definitions were more likely to identify themselves as feminists, were more involved in political activities and slightly more of them had a history of depression and eating disorders. Lesbians who provided nonpolitical definitions were more likely to have children, to have been raised in a conservative religion, and to think that they were born as lesbians. Various interpretations of the categories of definitions are provided.