I am looking for any help, advice or tips in how to explain heterogeneity / heteroscedasticity to biologists in my department. In particular I want to explain why its important to look for it and deal with it if it exists, I was looking for opinions on the following questions.
- Does heterogeneity influence the reliability of random effect estimates? I am pretty sure it does, but I couldn't find a paper.
- How serious a problem is heterogeneity? I have found conflicting views on this, while some say that model standard errors etc. will be unreliable, I have also read that it is only a problem if the heterogeneity is severe. How severe is severe?
- Advice on modelling heterogeneity. Currently, I focus largely on the nlme package in R and the use of variance covariates, this is pretty simple and most people here use R so providing scripts is useful. I am also using the MCMCglmm package as well, but other suggestions are welcome, particularly for non-normal data.
- Any other suggestions are welcome.