Group size and diversity

Last registered on September 19, 2022


Trial Information

General Information

Group size and diversity
Initial registration date
September 19, 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
September 19, 2022, 2:57 PM EDT

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



Primary Investigator

NOVAFRICA and Bissau Economics Lab

Other Primary Investigator(s)

PI Affiliation
University of Virginia
PI Affiliation
Bocconi University

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
In this paper we analyse the relationship between group size and the effect of diversity on workers’ performance. We focus on diversity in skills, but also investigate the additional impact of diversity in gender on performance. First, we explore the link between diversity and group size theoretically in a model with knowledge spillovers in production, which predicts that the effect of diversity (in skills) on individual performance increases with group size. We test this hypothesis in a lab experiment in Guinea-Bissau. Nursing and Economics students solve an individual test twice, first in isolation and then communicating with other participants, in homogeneous and diverse groups of different sizes. Our main outcome variable is the change in the percentage of correct answers between the two tests taken by a given individual. We test whether this change is positive and largest when the respondent works in larger and diverse groups compared to smaller homogeneous - or diverse - groups. We additionally ask whether the effect of skills diversity on performance is affected when accompanied by gender diversity, and whether this interaction is different in small or large groups and for male or female respondents.
External Link(s)

Registration Citation

Aman-Rana, Shan, Alexia Delfino and Brais Álvarez Pereira. 2022. "Group size and diversity." AEA RCT Registry. September 19.
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Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Each participant repeats a test made of 25 multiple-choice questions twice, first in isolation and then in a group (with experimentally-varied composition). The main outcome variable is the difference in the % of correct answers between the second (in group) and first (in isolation) test rounds. The % of correct answers is computed as the number of correct answers over 25 (multiplying by 100). Each question had five options and a unique correct answer: the first 10 were general-knowledge questions; the next 5 were questions from the other discipline (economics questions for nurses and nursing questions for economists); the last ten were questions from the participant’s field of study (nursing for nurses and economics for economists).
We analyse the results overall and by splitting the sample by gender of the test-takers (our stratification variable).
Our participants are both nurses and economists. However, economists are mainly used as sources of variation in team diversity (see treatments below), thus the analysis focuses on the outcomes for nurses.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
- Split of main outcome variables by knowledge area of the questions
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The design simultaneously studies three factors that could affect performance: team size, skill diversity, and gender diversity. With this aim, for the second round of the test, participants were randomly distributed into teams of size 2 or 4, composed only of nurses or of nurses with one economist of either gender.
Thus, in total, we have the following 6 types of groups:
- size 2, skill and gender homogeneous
- size 4, skill and gender homogeneous
- size 2, skill heterogeneous and gender homogeneous
- size 4, skill heterogeneous and gender homogeneous
- size 2, skill heterogeneous and gender heterogeneous
- size 4, skill heterogeneous and gender heterogeneous
We have both male and female nurses in the experiment, and will look at effects overall and splitting the sample by gender.
Experimental Design Details
Randomization Method
Administrative lists were used to randomize invites to participants (randomisation done in the back office using computer). Those who came to the university on the day of the experiment were randomized in a public lottery, stratified by gender.
Randomization Unit
Individuals randomised into different types of groups.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
86 clusters (experimental groups)
Sample size: planned number of observations
258 participants
Sample size (or number of clusters) by treatment arms
86 teams / 6 treatments = 14.3 groups by treatment
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
University of Virginia (UVA)
IRB Approval Date
IRB Approval Number
IRB Name
Universidade Lusófona da Guiné - ULG, Departamento de Economia e Gestão
IRB Approval Date
IRB Approval Number


Post Trial Information

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials