Journal Article

On the meta-analysis of response ratios for studies with correlated and multi-group designs

Lajeunesse, Marc J.

2011

Overview

A common effect size metric used to quantify the outcome of experiments for ecological meta-analysis is the response ratio (RR): the log proportional change in the means of a treatment and control group. Estimates of the variance of RR are also important for meta-analysis because they serve as weights when effect sizes are averaged and compared. The variance of an effect size is typically a function of sampling error; however, it can also be influenced by study design. Here, I derive new variances and covariances for RR for several often-encountered experimental designs: when the treatment and control means are correlated; when multiple treatments have a common control; when means are based on repeated measures; and when the study has a correlated factorial design, or is multivariate. These developments are useful for improving the quality of data extracted from studies for meta-analysis and help address some of the common challenges meta-analysts face when quantifying a diversity of experimental designs with the response ratio.

• Publisher: Ecological Society of America
• Subject: Animal and plant ecology / Animal, plant and microbial ecology / Biological and medical sciences / Covariance / Covariance matrices / Data Interpretation, Statistical / Ecological competition / Ecology / Ecology - methods / Ecophysiology / Ecosystem / Experiment design / experimental design / Fundamental and applied biological sciences. Psychology / General aspects / generalized least squares / large-sample theory / log response ratio / Meta analysis / Meta-Analysis as Topic / multivariate effect size / nonindependence / Research Design / Statistical discrepancies / Statistical variance / variance / variance-covariance matrix / weighted regression / Wetland ecology