You run a regression of child test scores on their parent's income level and find a positive effect. You believe that due to an omitted variable, you have an underestimate of this effect. If you have a relevant and exogenous instrument for parental income, what would you expect to happen to the coefficient on parent's income when you instrument for it?
A. It should get bigger
B. It should stay the same
C. It should get smaller
D. It should flip sign
Answer: A. It should get bigger