Introduction to Econometrics 3rd Edition by James Stock, Mark Watson

Exercise 4

Researchers studying the STAR data report anecdotal evidence that school principals were pressured by some parents to place their children in the small classes. Suppose that some principals succumbed to this pressure and transferred some children into the small classes. How would such transfers compromise the internal'validity of the study Suppose that you had data on the original random assignment of each student before the principal's intervention. How could you use this information to restore the internal-validity of the study