Dear Wolfgang , I am working with a meta-analysis in R (metafor package) using a mixed model framework to examine experimental effects of rodent seed predation on plant recruitment as a function of various plant species characteristics. I decided to go with metafor given that this allowed to account for random factors (specifically the study source, each of which typically estimated effects for multiple species) while testing for the influence of multiple fixed factors in the same model. The one snag I?ve hit concerns deriving estimates of the mean effect size (the response) for my two classes of ?status? (native or exotic) while accounting for the values of the continuous covariate ?logmass.? From playing with another meta-analysis package (OpenMEE, an interface that relies on the R package meta.analysis, which does not allow the addition of random factors). How I can estimate the mean effect size for "status" (alien and native) representative logmass values? Can I use the equation? But I?m unclear how I would calculate the associated SE for each estimate. Could the solution possibly be as easy as a simple equation that you already have?? Best
?ukasz Dylewski, M. Sc. PhD Student Department of Zoology, Institute of Zoology Pozna? University of Life Sciences Wojska Polskiego 71C 60-625 Pozna?, Poland http://ecology1.wixsite.com/farmlandecology [[alternative HTML version deleted]]