Predicting objective physical activity from self-report surveys: a model validation study using estimated generalized least-squares regression

Physical activity measurements derived from self-report surveys are prone to measurement errors. Monitoring devices like accelerometers offer more objective measurements of physical activity, but are impractical for use in large-scale surveys. A model capable of predicting objective measurements of physical activity from self-reports would offer a practical alternative to obtaining measurements directly from monitoring devices. Using data from National Health and Nutrition Examination Survey 2003–2006, we developed and validated models for predicting objective physical activity from self-report variables and other demographic characteristics. The prediction intervals produced by the models were large, suggesting that the ability to predict objective physical activity for individuals from self-reports is limited.     

Measures of biomarker dependence using a copula-based multivariate epsilon–skew–normal family of distributions

In this note we develop a new multivariate copula model based on epsilon–skew–normal marginal densities for the purpose of examining biomarker dependency structures. We illustrate the flexibility and utility of this model via a variety of graphical tools and a data analysis example pertaining to salivary biomarker. The multivariate normal model is a sub-model of the multivariate epsilon–skew–normal distribution.     

Likelihood‐based inferences about the mean area under a longitudinal curve in the presence of observations subject to limits of detection

Comparison of groups in longitudinal studies is often conducted using the area under the outcome versus time curve. However, outcomes may be subject to censoring due to a limit of detection and specific methods that take informative missingness into account need to be applied. In this article, we present a unified model‐based method that accounts for both the within‐subject variability in the estimation of the area under the curve as well as the missingness mechanism in the event of censoring. Simulation results demonstrate that our proposed method has a significant advantage over traditionally implemented methods with regards to its inferential properties. A working example from an AIDS study is presented to demonstrate the applicability of our approach. Copyright © 2015 John Wiley & Sons, Ltd.     

An Investigation of Indoor Air Contamination in Residences Above Dry Cleaners

An investigation of residences located above dry cleaning facilities was conducted to determine whether indoor and outdoor air concentrations of the dry cleaning solvent tetrachloroethene (perchloroethylene, PCE) were elevated compared to residences not near a dry cleaning facility. Data were also collected on the dry cleaners' operating conditions and equipment. Significantly elevated levels of PCE were found in the indoor air of each of six apartments located above dry cleaners compared to control residences for both day and night samples. The PCE concentrations in outdoor air near the dry cleaners were also significantly elevated compared to control locations and were lower than the concentrations measured indoors. The type of dry cleaning machine was significantly associated with the concentration of PCE found in the apartment above. A strong correlation was also found between the day and night PCE levels in the study apartments.     

Labour Surplus,Worker Rights and Productivity Growth: A Comparative Analysis of Asia and Latin America

How do labour market conditions, trade union rights and job security regulations affect labour productivity? This paper is the first attempt at an empirical analysis of this important question for a large sample of Asian and Latin American countries. We provide new estimates of the rates of surplus labour in 20 countries, as well as detailed tables summarizing their key regulations governing certain aspects of union activity and layoffs. Then we exploit these and other data in an econometric analysis of intercountry differentials in the growth rate of labour productivity in manufacturing during the 1980s. Among the principal results, we find that, while all else remains the same, productivity growth rates are significantly higher in countries with relatively larger labour surpluses, the effects of excess of labour on productivity growth are affected by the strength or weakness of union rights. We also find that the impacts of union rights and job security protections on productivity trends may be either positive or negative, depending on the labour market situation.     

Intermediate Performance Impacts of Advanced Manufacturing Technology Systems: An Empirical Investigation*

A large-scale random sample is used to empirically examine the relationships between implementation of Advanced Manufacturing Technology (AMT) and three organization-level measures that have historically been attributed to AMT, but not fully tested along the AMT spectrum: market-oriented flexibility of the production process, organizational integration of production processes, and administrative intensity of the organization. Results indicate that as an organization moves along the technology scale from stand-alone AMT (e.g., CNC machines) through functionally oriented AMT (FMS and CAM) toward CIM, not only do its production processes become more integrated with each other, but those processes become more integrated with other functional systems of the organization, and the quality and timeliness of production information increase. Furthermore, this relationship becomes stronger as companies increase their level of implementation for the latter two technologies. Conversely, market-oriented flexibility decreases and administrative intensity is not observed to change as companies move along the technology spectrum. Future research should examine how organizational redesign and implementation strategies that accompany AMT implementation can concomitantly enhance organizational integration of the production process and market-oriented flexibility.     

THE INDUCE VERSUS PURCHASE DECISION: AN EMPIRICAL ANALYSIS OF INDUSTRIAL R&D*

With the recent slowdown in productivity growth within the economy, R&D has come under scrutiny as a policy target variable. If such targeting is to be effective, it must be realized that not all innovations employed within a firm are induced by the firm through its own R&D: many innovations are purchased through technological licensing or in the form of new capital equipment. Here, interfirm differences in this “make” versus “buy” strategy are analyzed within the context of the Utterback-Abernathy production process lifecycle. Our findings suggest that (1) alternative sources to a firm's R&D for stimulating innovation may prove a viable strategy for federal targeting and (2) extrapolating the Utterback-Abernathy model to an industry formulation has empirical validity.     

WHAT MEASURE OF INFLATION SHOULD A CENTRAL BANK TARGET?

This paper assumes that a central bank commits itself to maintaining an inflation target and then asks what measure of the inflation rate the central bank should use if it wants to maximize economic stability. The paper first formalizes this problem and examines its microeconomic foundations. It then shows how the weight of a sector in the stability price index depends on the sector's characteristics, including size, cyclical sensitivity, sluggishness of price adjustment, and magnitude of sectoral shocks. When a numerical illustration of the problem is calibrated to U.S. data, one tentative conclusion is that a central bank that wants to achieve maximum stability of economic activity should use a price index that gives substantial weight to the level of nominal wages. (JEL: E42, E52, E58)