Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Principles behind instrumental variables analysis. (a) Classical instrumental variables design. (b) Comparing an instrumental variable to a randomized controlled trial reveals the problem of weak instruments. Weak instruments are those that randomly encourage members of the population to enter into a program or not, but many people can be noncompliant and not abide by the random encouragement.
