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Roommates and Peer Effects in the United States
Last registered on March 24, 2017

Pre-Trial

Trial Information
General Information
Title
Roommates and Peer Effects in the United States
RCT ID
AEARCTR-0002116
Initial registration date
March 24, 2017
Last updated
March 24, 2017 3:38 PM EDT
Location(s)
Primary Investigator
Affiliation
Dartmouth College
Other Primary Investigator(s)
Additional Trial Information
Status
Completed
Start date
1997-01-01
End date
2001-05-31
Secondary IDs
Abstract
The paper analyzes how peer effects relate to grade point average and decisions to join social groups such as fraternities. The results of the experiment indicate that residential peer effects are absent from major life decisions such as choice of college major. However, peer effects in GPA occur at the individual room level. Peer effects regarding fraternity membership occur both at the room level, whereas peer effects in fraternity membership occur both at the room level and the entire dorm level.

External Link(s)
Registration Citation
Citation
Sacerdote, Bruce. 2017. "Roommates and Peer Effects in the United States." AEA RCT Registry. March 24. https://doi.org/10.1257/rct.2116-1.0.
Former Citation
Sacerdote, Bruce. 2017. "Roommates and Peer Effects in the United States." AEA RCT Registry. March 24. https://www.socialscienceregistry.org/trials/2116/history/15388.
Experimental Details
Interventions
Intervention(s)
The intervention consists of measuring peer effects on observational data and regressing own outcomes and behavior on peer outcomes and behavior. The researcher indicates several main difficulties with this type of experiment as individuals generally self-select into neighborhoods, groups or roommate pairs, blurring the line between selection effect and peer effect.

The data comes from Dartmouth's database of students and includes a full history of housing/dorm assignments and term-by-term academic performance. Pretreatment characteristics include SAT scores, high school class rank, public versus private high school, home state and an academic index created by the admissions office. The data used are for the graduating classes of 1997 and 1998.
Intervention Start Date
1997-01-01
Intervention End Date
1998-12-31
Primary Outcomes
Primary Outcomes (end points)
GPA, major choice, membership in a fraternity
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
The experiment is based on Dartmouth College freshmen who are randomly assigned to dorms and roommates, implying that a roommate's background variables are uncorrelated with own background characteristics.

As a natural experiment, the results indicate that the coefficient on roommate GPA is 0.12 and significant. However, this freshman roommate effect on GPA disappears by senior year. Own senior year GPA is not correlated with freshman year roommates' senior year GPA. Additionally, the roommate's pre-enrollment intention to graduate with honors has a positive and statistically significant effect on GPA. Regarding the major choice, the data show that randomly assigned roommates have no effect on major. And regarding membership in a fraternity, if a freshman roommate joins a fraternity then he is 8% more likely to do so and 27% of the roommate pairs join the same house. Thus, roommate peer effects are important influences in freshman year GPA and in decisions to join social organizations. Roommate effects are not important in determining choice of major.
Experimental Design Details
Randomization Method
Randomization done by housing system
Randomization Unit
individual
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
n/a
Sample size: planned number of observations
1589 students
Sample size (or number of clusters) by treatment arms
1589 students in total
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
Dartmouth
IRB Approval Date
2018-01-01
IRB Approval Number
Details not available
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
Yes
Intervention Completion Date
December 31, 1998, 12:00 AM +00:00
Is data collection complete?
Yes
Data Collection Completion Date
December 31, 1998, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
n/a
Was attrition correlated with treatment status?
No
Final Sample Size: Total Number of Observations
1589 individuals
Final Sample Size (or Number of Clusters) by Treatment Arms
1589 individuals total
Data Publication
Data Publication
Is public data available?
No
Program Files
Program Files
Reports and Papers
Preliminary Reports
Relevant Papers
Abstract
This paper uses a unique data set to measure peer effects among college roommates. Freshman year roommates and dormmates are randomly assigned at Dartmouth College. I find that peers have an impact on grade point average and on decisions to join social groups such as fraternities. Residential peer effects are markedly absent in other major life decisions such as choice of college major. Peer effects in GPA occur at the individual room level, whereas peer effects in fraternity membership occur both at the room level and the entire dorm level. Overall, the data provide strong evidence for the existence of peer effects in student outcomes.
Citation
Sacerdote, Bruce. 2001. "Peer Effects with Random Assignment: Results for Dartmouth Roommates." Quarterly Journal of Economics 116(2): 681-704.