Hi all,
I am trying the identify the outliers of a REML mixed model that includes two nominal fixed factors and one random factor. As shown in the screenshots below, the parity plot, residual by row plot and residual by predicted plot all clearly flagged six observations as strong outliers (black points). However, these outliers are not captured in studentized residual plot where their residuals are comparable to others (grey points) and are within the +/- 3 limits. In addition, by removing three of the outliers and refitting the model, everything looks completely fine and the other three observations initially identified as outliers are now well predicted by the model. Any inputs what might be the root causes for these cases? Thank you.
Refit the model after removing three of the outliers
