Save a contact, save your contacts: A natural field experiment of nudges for contact tracing participation

Last registered on February 14, 2023

Pre-Trial

Trial Information

General Information

Title
Save a contact, save your contacts: A natural field experiment of nudges for contact tracing participation
RCT ID
AEARCTR-0006990
Initial registration date
January 05, 2021

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
January 06, 2021, 10:02 AM EST

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

Last updated
February 14, 2023, 11:15 PM EST

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

Locations

Primary Investigator

Affiliation
University of Chicago

Other Primary Investigator(s)

PI Affiliation
University of Chicago

Additional Trial Information

Status
In development
Start date
2021-01-11
End date
2024-02-29
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
Mailing experiment to study what nudges work to improve participation in Covid-19 contact tracing.
External Link(s)

Registration Citation

Citation
Birke, David and Ariel Listo. 2023. "Save a contact, save your contacts: A natural field experiment of nudges for contact tracing participation." AEA RCT Registry. February 14. https://doi.org/10.1257/rct.6990-1.2
Experimental Details

Interventions

Intervention(s)
Intervention Start Date
2021-01-11
Intervention End Date
2021-02-28

Primary Outcomes

Primary Outcomes (end points)
In collaboration with the city's health department, we measure response rates and completion of initial and follow-up contact tracing calls and interviews, separately for both positively tested cases and high-risk contacts. We link these outcomes to postal routes using individual residential addresses.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
N/A
Experimental Design Details
We randomize USPS postal routes within the metropolitan area of Louisville, KY into receiving different versions of postcards that prompt residents to pick up their phones when they receive a call from the contact-tracing team of the Louisville Department of Public Health and Wellness. Once a postal route is selected into treatment, all residential households within that route will receive a postcard.

Postal routes are assigned either to a control group or to one of six treatment groups that differ in the postcard design.

The six postcard designs are identical in the following:
- Inform about Louisville contact tracing
- Ask to save contact tracing number to phone contacts + QR code
- Ask to answer phone when receiving call

The six postcard designs differ in the following:
- Message and visual elements on front: (a) “This is not spam”, (b) “Save a number, save a life”, (c) “Let’s get open”
- Phone no. shown: (i) 502.912.8968, (ii) 502.912.8982

We cross-randomize these elements in a 3x2 design. We assign 6 x 54 = 324 postal routes to one of the six treatment conditions and the remaining 652 - 324 = 328 postal routes to control. We assign an approximately equal number of treatments assigned to each route within each zip code.

We plan to send out the first batch of postcard in early January 2021. We plan to send out a second batch of postcards in late January or February. We will update this pre-registration before sending out the second batch of postcards.
Randomization Method
Done by a computer, see attached code
Randomization Unit
Treatment is assigned to postal routes. Outcomes are observed at the individual level, which is linked to the postal route using the individual's residential address.
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
652 postal routes
Sample size: planned number of observations
Approximately 20,000-50,000 cases or contacts, depending on the number of cases and high-risk contacts that will be reported to the city's contact tracing team over January and February. Additional observations will come from retrospective pre-treatment data.
Sample size (or number of clusters) by treatment arms
Around half in control and 1/12 in each of the 6 treatments. Exact number will depend on the number of cases and high-risk contacts that will be reported to the city's contact tracing team.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials

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IRB

Institutional Review Boards (IRBs)

IRB Name
The University of Chicago Institutional Review Board
IRB Approval Date
2020-12-22
IRB Approval Number
IRB20-2101
Analysis Plan

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Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
No
Data Collection Complete
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials