Recall that the researchers modeled mean income, E(y), as a function of both agreeableness score (x1) and

Question:

Recall that the researchers modeled mean income, E(y), as a function of both agreeableness score (x1) and a dummy variable for gender (x2 = 1 if male, 0 if female). Use the data saved in the file to analyze the residuals of the model.
E(y) = β0 + β1x1 + (β2x1)2 + β3x2
What model modifications, if any, do you recommend?
For information: Refer to the Journal of Personality and Social Psychology (Feb. 2012) study of on-the-job agreeableness and wages. Exercise 12.107.