Might anyone know why, when running multilevel (mixed effects) models with REML I get completely different results when I run the same models with robust variances? I originally chose REML because I have a small number of clusters (11). However, when plotting the residuals for a particular model, it was clear that they were nowhere near normally distributed. I re-ran the model using robust standard errors (the robust option is not available with REML in stata), and the results were completely different. Can anyone explain why this might be?

TIA.