I am trying to do mixed effect regression model with lme4.lmer function. The model has two fixed categorical variables, one random categorical variable and response is continuous variable (distance in meters). I am just puzzled with this residual plot.
I would like to ask:
1.) may I assume from this plot that the model is linear?
2.) there is heteroskedasticity, since variability in residual for smaller values is lower than for bigger values?
3.) According to points 1 and 2, can I use this method, or should I make some log transformation on response and check if this plot looks better, or should I use som other type of model (which?).