An experiment about discrimination

Last registered on September 21, 2023


Trial Information

General Information

An experiment about discrimination
Initial registration date
May 27, 2022

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
May 30, 2022, 8:13 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
September 21, 2023, 8:39 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

São Paulo School of Economics Fundação Getulio Vargas

Other Primary Investigator(s)

PI Affiliation
São Paulo School of Economics Fundação Getulio Vargas
PI Affiliation
São Paulo School of Economics Fundação Getulio Vargas

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
We design an experiment to test for discrimination.
External Link(s)

Registration Citation

Ajzenman, Nicolás, Bruno Ferman and Pedro Sant'Anna. 2023. "An experiment about discrimination." AEA RCT Registry. September 21.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
See pre-analysis plan
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
See pre-analysis plan
Experimental Design Details
We create fictitious accounts on Twitter that resemble humans and that claim to be PhD students with interests in topics related to economics. The accounts differ on three observable characteristics: gender (male or female), race (black or white) and university affiliation (highly ranked or not). The accounts follow approximately 100 subjects who are part of the "EconTwitter" community. After being active for twelve days, we measure how many follow backs each bot account obtained.

Our subject pool is composed of all Twitter accounts that either tweeted or re-tweeted a status containing the term "#EconTwitter" between January 1st and February 28th, 2022 (approximately 15,000 accounts). Then, we will create 240 fictitious accounts claiming to be PhD students and who differ in their gender, race and university affiliation (overall, we have 30 accounts of each group). Each account will be active for a period of twelve days and follow approximately 100 subjects from the ‘EconTwitter’ sample. Our main outcome is whether or not
each subject followed back the bot accounts. Given that the accounts are identical in all respects but in the three dimensions we varied, differences in follow-back associated with the groups will be due to discrimination.

The experiment will be conducted in 30 waves of twelve days. In each wave, 8 accounts will be active. They will follow their respective subjects on the first day of activation, and we will measure follow-backs twice a day.

The subjects followed by each bot account will be defined randomly. Specifically, we perform block randomization as a way to improve balance. For the block randomization, we will use the following variables: gender (male, female, missing); profession (professor; graduate student; other; missing); the number of followers (above or below median). This gives us 24 strata. We will sample randomly from within each stratum, assigning the same proportion of users in each stratum to each bot account. Specifically, each bot account will be assigned to approximately 100 accounts to follow.
Randomization Method
Randomization done in office by a computer
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
240 accounts
Sample size: planned number of observations
24000 subjects (individuals)
Sample size (or number of clusters) by treatment arms
3000 subjects
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Ethical Compliance Committee on Research Involving Human Beings of Fundaçao Getulio Vargas
IRB Approval Date
IRB Approval Number
Opinion n. 034/2022
Analysis Plan

Analysis Plan Documents


MD5: 76e58f0326c1659cd89d0963651d442b

SHA1: 79ef79a9028cbd970fbcf91f47cb248a8954cee6

Uploaded At: August 12, 2022


Post Trial Information

Study Withdrawal

There is information in this trial unavailable to the public. Use the button below to request access.

Request Information


Is the intervention completed?
Intervention Completion Date
August 12, 2022, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
August 12, 2022, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
80 bot-wave pairs
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
6920 econtwitter accounts
Final Sample Size (or Number of Clusters) by Treatment Arms
approximately 900 accounts per treatment arm (bot type)
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials