I am doing a multiple regression analysis regressing GPA against several 0/1 indicator variables (representing course completions). My fitted vs. residual plot is biased and looks awful. See below. Is there some way to make this better besides adding more predictors?
Also, I am not trying to do any prediction. I only want to know if the predictors are significant and what their effect size is (strength of relationship). So, how would the biased residuals affect this?
Any help is appreciated. Thanks!!