Using Observational vs. Randomized Controlled Trial Data to Learn About Treatment Effects
39 Pages Posted: 18 Apr 2011
Date Written: April 14, 2011
Abstract
Randomized controlled trials (RCTs) are routinely used in medicine and are becoming more popular in economics. Data from RCTs are used to learn about treatment effects of interest. This paper studies what one can learn about the average treatment response (ATR) and average treatment effect (ATE) from RCT data under various assumptions and compares that to using observational data. We find that data from an RCT need not point identify the ATR or ATE because of selection into an RCT, as subjects are not randomly assigned from the population of interest to participate in the RCT. This problem relating to external validity is the primary problem we study. So, assuming internal validity of the RCT, we study the identified features of these treatment effects under a variety of weak assumptions such as: mean independence of response from participation, an instrumental variable assumption, or that there is a linear effect of participation on response. In particular we provide assumptions sufficient to point identify the ATR or the ATE from RCT data and also shed light on when the sign of the ATE can be identified. We then characterize assumptions under which RCT data provide more information than observational data.
Suggested Citation: Suggested Citation
Do you have a job opening that you would like to promote on SSRN?
Recommended Papers
-
Vouchers for Private Schooling in Colombia: Evidence from a Randomized Natural Experiment
By Joshua D. Angrist, Eric Bettinger, ...
-
Remedying Education: Evidence from Two Randomized Experiments in India
By Shawn Allen Cole, Abhijit V. Banerjee, ...
-
Remedying Education: Evidence from Two Randomized Experiments in India
By Abhijit V. Banerjee, Esther Duflo, ...
-
By Michael Kremer, Edward Miguel, ...
-
By Michael Kremer, Edward Miguel, ...
-
By Michael Kremer, Edward Miguel, ...
-
Using Randomization in Development Economics Research: A Toolkit
By Esther Duflo, Rachel Glennerster, ...
-
Using Randomization in Development Economics Research: A Toolkit
By Esther Duflo, Rachel Glennerster, ...
-
Using Randomization in Development Economics Research: A Toolkit
By Esther Duflo, Rachel Glennerster, ...
-
Monitoring Works: Getting Teachers to Come to School
By Esther Duflo and Rema Hanna