Default Bias and Preference for Randomization

Last registered on April 10, 2024


Trial Information

General Information

Default Bias and Preference for Randomization
Initial registration date
April 03, 2024

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
April 09, 2024, 5:06 PM EDT

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

Last updated
April 10, 2024, 4:27 AM EDT

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


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

Request Information

Primary Investigator

Sungkyunkwan University

Other Primary Investigator(s)

PI Affiliation
Hong Kong University of Science and Technology

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Using an online experiment, we investigate when people are likely to commit default bias in decision-making and whether offering a coin-flipping option can mitigate the default bias. The participants engage in a series of decision-making tasks, choosing between two lotteries. One lottery is provided as the default option and they must decide whether to keep the default option or trade for another lottery. The participants are randomly assigned to a control condition and a treatment condition, where they can toss a coin to make the decision. We further vary the statistical relationship between the two lotteries and measure participants’ attentiveness. We seek to answer the following questions: 1) Do the statistical relationships between the two lotteries affect the tendency to commit the default bias and the tendency of choosing coin-flipping? 2) Does participants’ attentiveness affect committing the default bias and the tendency of choosing coin-flipping? 3) When coin-flipping is more likely to mitigate the default bias?
External Link(s)

Registration Citation

Zhang, Xing and Songfa Zhong. 2024. "Default Bias and Preference for Randomization ." AEA RCT Registry. April 10.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
The default bias by experimental conditions, attentiveness, and statistical relationship of the two lotteries;
The choice of coin-flipping option by attentiveness and statistical relationship of the two lotteries.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Correlation of default bias and the choice of coin-flipping by the same individual (attentive vs. inattentive) across different statistical relationships.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The experiment will be conducted on the online survey platform Qualtrics. Participants will be recruited on Prolific. They will receive a fixed show-up fee and be given an experiment stock as a bonus. The return for stock is determined as follows: A computer will randomly draw one card from a set of 4 cards, which includes 1 red card, 1 white card, 1 black card, and 1 blue card. Depending on which card is drawn, the stock will pay a certain amount of money. For example, suppose the following stock (namely, Stock A) is given to the participant:

• If the red card is drawn, the participant will receive a return of $15.
• If the white card is drawn, the participant will receive a return of $2.
• If the black card is drawn, the participant will receive a return of $0.
• If the blue card is drawn, the participant will receive a return of $8.

The participant can keep Stock A, i.e., choose the default, or she can trade the stock for another stock (namely, Stock B). The experiment follows a mixed design including a between-subject factor (Coin vs. No Coin) and a within-subject factor (Stock A is the default vs. Stock B is the default). When a participant chooses to keep Stock A when Stock A is the default but chooses to keep Stock B when Stock B is the default, we consider this participant commits default bias facing Stock A and B.

At the end of the experiment, we select 5 choice tasks they did, and ask them to recall their decisions. Each decision that was successfully recalled would receive US$0.2.

The following information will also be collected from the participants:
1. Response time
2. Demographic information (gender, age, education, employment, and religion)
Experimental Design Details
Not available
Randomization Method
Treatment group assignment will be randomized by the Qualtrics online software.
Randomization Unit
Individual participant.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Around 240 participants.
Sample size: planned number of observations
Around 240 X 60 = 14,400 (number of participants X number of tasks).
Sample size (or number of clusters) by treatment arms
Around 120 participants.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Department of Economics Ethics Review Committee at National University of Singapore
IRB Approval Date
IRB Approval Number