Hartung-Knapp-Sidik-Jonkman approach and its modification for random-effects meta-analysis with few studies

Background Random-effects meta-analysis is commonly performed by first deriving an estimate of the between-study variation, the heterogeneity, and subsequently using this as the basis for combining results, i.e., for estimating the effect, the figure of primary interest. The heterogeneity variance estimate however is commonly associated with substantial uncertainty, especially in contexts where there are only few studies available, such as in small populations and rare diseases. Methods Confidence intervals and tests for the effect may be constructed via a simple normal approximation, or via a Student-t distribution, using the Hartung-Knapp-Sidik-Jonkman (HKSJ) approach, which additionally uses a refined estimator of variance of the effect estimator. The modified Knapp-Hartung method (mKH) applies an ad hoc correction and has been proposed to prevent counterintuitive effects and to yield more conservative inference. We performed a simulation study to investigate the behaviour of the standard HKSJ and modified mKH procedures in a range of circumstances, with a focus on the common case of meta-analysis based on only a few studies. Results The standard HKSJ procedure works well when the treatment effect estimates to be combined are of comparable precision, but nominal error levels are exceeded when standard errors vary considerably between studies (e.g. due to variations in study size). Application of the modification on the other hand yields more conservative results with error rates closer to the nominal level. Differences are most pronounced in the common case of few studies of varying size or precision. Conclusions Use of the modified mKH procedure is recommended, especially when only a few studies contribute to the meta-analysis and the involved studies’ precisions (standard errors) vary.peerReviewe

Corporate governance and intellectual capital reporting in a period of financial crisis: evidence from Portugal

This paper uses an analytical frame comprised of agency theory and a resource based perspective to explore the influence of boards of directors on listed companies’ voluntary disclosure of information concerning intellectual capital [IC]. The IC disclosures in 75 published company reports of 15 listed Portuguese companies in a five year period of financial crisis, 2007 to 2011, are investigated using content analysis and regression techniques. IC disclosures are found to increase with company size, dual corporate governance models, industry, listing on sustainability indexes, and increases in board size up to a maximum point (beyond which disclosures decrease). IC disclosures are reduced by CEO duality and by a higher proportion of independent directors on boards. The year of reporting is not significant, suggesting that the period of financial crisis did not influence the level of IC disclosures. The evidence adduced is consistent with a view that highly visible companies acknowledge the importance of IC disclosures in maintaining their reputation and competitive advantage, even during a period of financial crisis. This paper highlights the need for caution in believing that adding extra directors to an existing board will lead to improved disclosure outcomes. Additionally, given the token number of females appointed to boards currently, the Portuguese capital market regulator should consider enforcing measures to ensure compliance with EU objectives.info:eu-repo/semantics/publishedVersio