Celebrity endorsement in promoting pro-environmental behavior
Last registered on January 24, 2020


Trial Information
General Information
Celebrity endorsement in promoting pro-environmental behavior
Initial registration date
October 23, 2019
Last updated
January 24, 2020 3:01 AM EST

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Primary Investigator
School of Economics, University of Economics Ho Chi Minh City
Other Primary Investigator(s)
PI Affiliation
Department of Economics, University of Gothenburg, Sweden
PI Affiliation
Economics and Environment for Development Research Program, CATIE, Costa Rica
PI Affiliation
Department of Social Sciences, Wageningen University and Research, The Netherlands
PI Affiliation
School of Economics, University of Economics Ho Chi Minh City, Vietnam
PI Affiliation
Department of Economics, University of Gothenburg, Sweden
Additional Trial Information
In development
Start date
End date
Secondary IDs
There is greatly growing attention to tackle plastic pollution issues. Previous studies proposed various instruments dealing with the plastic problems. Education and information programs are frequently used and examined as a mean promoting pro-environmental behavior. Several different forms of pro-environmental campaigns have been observed, i.e., public engagement activities with the participation of celebrities. However, very little research evaluating those activities or investigating different channels of delivering information to the public, hence enhancing behavior change. These are expected to demonstrate through the current study using field experiments to examine the change in knowledge, attitudes and behavior towards plastic consumption. A sample of 1,560 students living in two largest dormitory systems in Ho Chi Minh City and the Mekong River Delta of Vietnam is collected. There are a control group and three add-on treatment groups including environmental education, celebrity endorsement and personal pledge. Two video clips are designed to serve as the environmental education and celebrity treatments. The personal pledge takes a form of a commitment card delivered to the participant asked to join the celebrity in reducing plastic consumption. The treatment is delivered in a workshop form of about 25 participants each. Each participant will receive a voucher framed as compensation for participation in each stage of the study. The participant will redeem the voucher at an experimental shop. It is designed as an instrument to measure student’s behavior before and after the treatment. In addition, we expect to examine the spill-over effect on other domains, i.e., behavior changes made by the participants’ roommates, using a follow-up survey. Specially, a variation of a dictator game is employed to measure individual’s willingness to contribute to an environmental fund that helps triggering pro-environmental behavior. Various econometric models to examine the treatment effect are expected to provide direct and indirect effect of the treatment as well as relative effect among the different channels. This reveals evidence to inform policy options for behavior changes towards plastic pollution mitigation.

External Link(s)
Registration Citation
Alpizar, Francisco et al. 2020. "Celebrity endorsement in promoting pro-environmental behavior." AEA RCT Registry. January 24. https://doi.org/10.1257/rct.4859-1.1.
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Experimental Details
There are three primary add-on interventions and a market tool that are being introduced through out this study. The primary interventions included environmental education (EE), celebrity endorsement (CE), and individual pledge by providing a commitment card for the treated participant with the celebrity's signature showing her commitment. The market tool intervention is to introduce a tax policy imposing on the use of single-use plastic items.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
Outcomes of interest and measures of outcomes
We are interested in the changes of knowledge, attitude and practices (KAP) of students regarding plastics pollution and general environmental issues. These are the direct outcomes of our intervention on plastic pollution, and the changes of KAPs regarding general/other environmental issues as the indirect outcomes. Knowledge on marine plastic pollution (MPP) issues are measured by student surveys. EE is expected to increase knowledge. Change in knowledge is a validity test of our EE intervention. Attitudes toward MPP issues are also measured by student surveys. EE is expected to lead to more positive attitudes toward environmental issues. Practices that help mitigate MPP issues are measured through both self-reported behavior in surveys and behavior observed in the field using field experiments. Changes in behavior is the key outcome because our intervention is aimed to influence.
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
We introduce an shop experiment to observe the consumption behavior of the participant toward plastic issues. Each participant will be offered a gift voucher of 110,000 VND to trade a fixed set of good items. This includes some packed milk, yogurt boxes, instant noodle packages, some candies, pens and a soft drink. These are among the most commonly consumed by students and the bundle of goods may require some single-plastic items, i.e., bags, straws and spoons.
Experimental Design Details
Not available
Randomization Method
In order to reduce contamination of treatment and study potential spillover effects of the treatment, our treatment assignment is randomized at dormitory room level. We use all the undergraduate dormitory rooms as our sampling frame. We randomly select rooms for the study and randomly assign selected rooms to the treatment or control groups. We randomly select one student in each room as participants of the workshops, as our research subjects for the study of direct effects and randomly one of their roommates in each room for the study of spillover effects. Given we only pick one student in each room, within our sample, randomization occurs at individual level.
Randomization Unit
First sampled number of rooms are randomly selected. Then, in each room there is a student is randomly invited to participate in this study.
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
About 1,560 rooms
Sample size: planned number of observations
1,560 students
Sample size (or number of clusters) by treatment arms
390 students control, 390 students environmental education (EE), 390 students EE and celebrity endorsement (CE), 390 students EE, CE and individual pledge.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Given that we have a relatively large sample in each treatment arm and we randomize the treatment allocation at individual level, , our experiment is able to detect relatively small effect size. Note that despite we collect panel data for the estimating the direct effect on the workshop participants, we can only test some other hypotheses with post-intervention cross-sectional data. Therefore, we calculate the minimum detectable effect sizes conservatively assuming we only have post-intervention cross-sectional data. For a binary outcome variable, such as use single-use plastics or not, assuming that 90% of the participants in the control group takes use single-use plastics and there and the attrition rate is 10%, we can detect a reduction by 8 percentage points using a two-sided chi-squared test with a statistical power of 0.8 at the significant level of 0.05. For a continuous outcome variable like the amount fo donation to an environmental NGO, we can detect an effect that equals to 21% of the standard deviation of the donations in the control group using a two-sided t-test with a power of 0.8 at the significant level of 0.05. The minimum detectable effect size is much smaller that the effects found in studies that examines the effects of educational video on pro-environmental behavioral (e.g. Giglio et al. 2018).
Supporting Documents and Materials

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IRB Name
University of Economics Ho Chi Minh City, Vietnam
IRB Approval Date
IRB Approval Number
Analysis Plan

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