I'm having a bit of difficulty getting a clear understanding of what should be considered a fixed vs. a random effect in a linear mixed model analysis of field data. Even the statisticians seem to say "it depends on who's defining it" or "sometimes the same treatment/variable can be either". Some examples may help, let's say I collected samples annually in three sites and wanted to test for the effect of daily rainfall, daily temperature, and density, on recruitment of individuals in the following year. Using the lmer function in R which of these would be fixed effects and which would be random? A reference or two would help. I really couldn't find much in a google search on field studies, but I didn't go to anything like zoological abstracts. TIA, g2
-- Gary D. Grossman, PhD Fellow, American Fisheries Soc. Professor of Animal Ecology Warnell School of Forestry & Natural Resources University of Georgia Athens, GA, USA 30602 Website - Science, Art (G. Grossman Fine Art) and Music www.garygrossman.net Board of Editors - Animal Biodiversity and Conservation Editorial Board - Freshwater Biology Editorial Board - Ecology Freshwater Fish Hutson Gallery Provincetown, MA - www.hutsongallery.net/artists.html
