Dr. Smart is studying the relation between the percentage of a population who has a PhD degree (X) and the average income (Y) in 108 cities. After fitting a simple linear regression model, he decides to assess whether the assumptions of the model are reasonably satisfied. Below is one of the plots he uses to assess the assumptions.

What assumption(s) is Dr. Smart trying to assess using this plot?

Based on the plot, is there any indication of assumption violations? If so, which

assumption(s) has (have) been violated?

What are the possible consequences of the assumption violation(s)?

Suggest at least one solution to fix the problem.