Proper manual handling techniques to prevent low back pain, a Cochrane systematic review

Training and provision of assistive devices are considered major interventions to prevent and treat low back pain (LBP) among workers exposed to manual material handling (MMH). To establish the effectiveness of training and provision of assistive devices in preventing and treating LBP an update of a Cochrane literature review was performed to November 2010. Randomised controlled trials (RCTs) and cohort studies with a concurrent control group (CCTs) were included. Nine RCTs (20.101 employees) and nine CCTs (1280 employees) were included for prevention: six more than in the previous version. No study on treatment was found. None of the included RCTs and CCTs provided evidence that training and provision of assistive devices prevented LBP when compared to no intervention or another intervention.     

The Tale of Cochran's Rule: My Contingency Table has so Many Expected Values Smaller than 5, What Am I to Do?

In an informal way, some dilemmas in connection with hypothesis testing in contingency tables are discussed. The body of the article concerns the numerical evaluation of Cochran's Rule about the minimum expected value in r × c contingency tables with fixed margins when testing independence with Pearson's X² statistic using the χ² distribution.     

Comments on “a generalization of fisher's exact test in pxq contingency tables using more concordant relations”

The purpose of this note is to criticize Nguyen (1985) for his account of the literature on the generalization of Fisher's exact test and to point out parallels with existing algorithms of the algorithm proposed by Nguyen. Subsequently we will briefly raise some questions on the methodology proposed by Nguyen.

Nguyen (1985) suggests that all literature on exact testing prior to Nguyen & Sampson (1985) is based on the “more probable” relation or Exact Probability Test (EPT) as a test statistic. This is not correct. Yates (1934 - Pearson's X²), Lewontin & Felsenstein (1965 - X²), Agresti & Wackerly (1977 - X², Kendall's tau, Kruskal & Goodman's gamma), Klotz (1966 - Wilcoxon), Klotz & Teng (1977 - Kruskall & Wallis' H), Larntz (1978 - X², loglike-lihood-ratio statistic G², Freeman & Tukey statistic), and several others have investigated exact tests with other statistics than the EPT. In fact, Bennett & Nakamura (1963) are incorrectly cited as they investigated both X² and G², rather than EPT. Also, Freeman & Halton (1951) are incorrectly cited for they generalized Fisher's exact test to pxq tables and not 2xq tables as stated. And they are even predated by Yates (1934) who extended the test to 2×3 tables.     

Measuring progress and evolution in science and technology – I: The multiple uses of bibliometric indicators

Science and technology development have become critical instruments in the public policy arena given their demonstrated impact on economic progress. As a consequence, a vast array of indicators for measuring and mapping scientific and technological activity, their progress and their outcomes, has been developed over recent decades (see for instance, the EU Commission, 2nd Report on S&T Indicators 1997). The majority of them relate to measuring and mapping the published journal and patent literature. The first part of this review paper focuses on a state–of–the–art overview of bibliometric indicators and their multiple uses in supporting the development of science and technology policy. The limitations and the pitfalls related to their use are also discussed.     

On opulence driven poverty traps

Endogenous population growth, i.e., making the rate of population growth dependent on society's opulence, causes parametric changes to have a larger impact and can cause multiplicity of steady states in a dynamic intertemporal optimization framework. This provides a simple explanation for the possibility of differing growth paths between countries (using a standard production function) or another explanation of the poverty trap. We give two examples (opulence sensitivity and production sensitivity) that both give rise to three steady states in which poor (rich) countries will evolve over time to the low (high) income steady state. In both examples there are middle income countries that will choose the low (high) income steady state if they are impatient (patient), where patience is measured through the rate of time preference o. Foreign aid in the form of a large transfer of capital from abroad enables poor and impatient middle income countries to move to the high income steady state.We would like to thank Nico Heering, Martijn Herrmann, Theo Junius, Ngo van Long, Ad Pikkemaat, John Pitchford, Lakshmi Raut, Casper de Vries, an anonymous referee, participants of workshops at the University of Groningen and the University of Amsterdam and especially Harry van Dalen for valuable comments. The article was presented at the fifth annual conference of the European Society of Population Economics, Pisa 1991. The views expressed in the article are those of the authors and not necessarily those of the World Bank.     

Low socioeconomic status increases effects of negative life events on antenatal anxiety and depression

Problem

Low socioeconomic status and prior negative life events are documented risk factors for antenatal anxiety and depression, preterm birth and birth weight. We aimed to asses whether the adverse effects of prior negative life events increase with lower socioeconomic status and which aspects of socioeconomic status are most relevant.

Marshall and Gorman's Markov chain model for occupational prestige

This report scrutinizes the Markov chain model for occupational prestige proposed by K. P. Marshall and B. L. Gorman (1975, Social Science Research 4, 41–64). It is shown that the results of their application are highly unstable.     

Measuring progress and evolution in science and technology – II: The multiple uses of technometric indicators

Science and technology development have become critical instruments in the public policy arena given their demonstrated impact on economic progress. As a consequence, a wide array of indicators for measuring and mapping scientific and technological activity, their progress and their outcomes, has been developed over recent decades (see for instance, European Commission, 2nd Report on S&T Indicators, 1997). The majority of these indicators relate to measuring and mapping the published journal and patent literature. In the second part of this review, we focus on a state-of-the-art overview of patent indicators and their multiple uses in supporting the development of science and technology policy. We also discuss the limitations and the pitfalls related to their use.     

Alternative transformations to eliminate fixed effects

In a panel data model with fixed individual effects, a number of alternative transformations are available to eliminate these effects such that the slope parameters can be estimated from ordinary least squares on transformed data. In this note we show that each transformation leads to algebraically the same estimator if the transformed data are used efficiently (i.e. if GLS is applied). If OLS is used, however, differences may occur and the routinely computed variances, even after degrees of freedom correction, are incorrect. In addition, it may matter whether “redundant” observations are used or not.