To estimate the impact of attending pre‐school on the probability of attending college, a researcher proposes to use a sibling fixed effects approach. Which of the following sources of omitted variable does this eliminate?
A. Children who attend pre‐school are from more educated families than children who do not.
B. Families send children to pre‐school only if those children are healthy.
C. Families send children to pre‐school when the economy is doing well.
D. None of the above.
Answer: A. Children who attend pre-school are from more educated families than children who do not.