On the one-sample location hypothesis for mixed bivariate data

We study a hypothesis testing problem involving the location model suggested by Olkin and Tate (1961). Specifically, we derive a likelihood ratio lest of the associated location hypothesis as an alternative to the conventional method of carrying out separate tests for each of the parameters. A small sample Monte Carlo comparison indicates the general superiority of the former in terms of statistical power. We also comment briefly on the properties of the test.     

Validity of work-related assessments

Insufficient evidence of the validity of work-related assessments is frequently reported as a major concern in occupational rehabilitation. Despite this concern, and the continuing development of new and old assessments, no comprehensive evaluation of the evidence has been conducted. OBJECTIVES: The purpose of this study was to first determine the extent and quality of available evidence for the validity of work-related assessments, and then where sufficient evidence was available, determine the level of validity. STUDY DESIGN: This study examined available literature and sources in order to review the extent to which validity has been established for 28 work-related assessments. RESULTS: The levels of evidence and validity are presented for each assessment. Most work-related assessments have limited evidence of validity. Of those that had adequate evidence, validity ranged from poor to good. There was no instrument that demonstrated moderate to good validity in all areas. Very few work-related assessments were able to demonstrate adequate validity in more than one area, or with more than one study, even when contributory evidence was included. CONCLUSION: With this study clinicians will be able to examine their options with regard to the validity of the assessments they choose to use.     

A review of research on techniques for lifting low-lying objects: 1. Criteria for evaluation

Advice and training on techniques for lifting is frequently provided. The choice of which technique to use should be based on the evidence available on a number of criteria. Important criteria include: psychophysical, physiological, biomechanical, psychological, performance and clinical. However few professionals have the time to read all the original research required to understand the limitations of the available criteria. The purpose of this paper was to present an accessible synthesis of the criteria used to choose a specific technique. Each criterion is described and its validity discussed to provide the reader with a better understanding of the criteria, and thus the evidence available.     

Impact of Hazardous Substances Regulations on Small Firms in Delaware and New Jersey

Regulations under the 1990 Amendments to the Clean Air Act impose significant requirements on firms handling hazardous chemicals. The nature of the regulations would suggest that small firms, because of limited resources and other structural limitations, would experience more difficulty complying with the regulations than large firms. To understand the difficulties imposed by the regulations on small firms, we interviewed ten small firms in Delaware and New Jersey, states with existing hazardous regulations similar to those being considered by the U.S. Environmental Protection Agency, and evaluated their responses to state regulations. The impacts of the environmental regulations on the firms and on the risk levels of their businesses are discussed. Propositions for research into small firms compliance are developed. Possible means for reducing the regulatory burden on small firms while enhancing regulatory effectiveness are suggested.     

Quality Provision with Heterogeneous Consumer Reservation Utilities

This study examines a firm's quality and price decisions when consumers differ not only in their willingness‐to‐pay for quality but also in their reservation utility for the basic product. We find that while the firm offers lower‐quality products when consumers' valuations for quality deteriorate, the optimal quality may increase with a negative shift in consumers' reservation utilities. We also investigate the optimal price and quality of the products within a vertically differentiated product line when the number of products is exogenously given. The existing literature shows that when consumers differ only in their willingness‐to‐pay for quality, the firm sets the efficient quality for consumers with the highest valuation for quality, whereas the concern for cannibalization pushes down the quality of inferior products. We find that when consumers are heterogeneous in both their reservation utility and valuation for quality, the concern for cannibalization may distort the quality upwards, even for consumers with the highest willingness‐to‐pay for quality. In addition, a low‐quality product may enjoy a higher profit margin than a high‐quality product within the product line.     

The Gamma Distribution as a Mixture of Exponential Distributions

A gamma distribution with arbitrary scale parameter θ and shape parameter r < 1 can be represented as a scale mixture of exponential distributions.