Instrumental Variables
Nick Huntington‐Klein · 2021
If you want to build a statue, one way to go about it is to get a big block of marble and chip away at it until you reveal the desired form underneath. Another way is to take something like concrete or molten steel, and pour it into a mold that only allows the desired form to show through. Research designs based on closing back doors and removing undesirable variation are sort of like the former. Instrumental variables designs are like the latter.