Experimental Design Details
Choosing celebrity
The candidate celebrity in this study is Hoang Thuy, who is best known for winning cycle 2 of Vietnam's Next Top Model. She is the first runner-up at the Miss Vietnam Universe 2017 pageant. She will represent Vietnam at the Miss Universe 2019 pageant. Our first pre-test with around 245 Vietnamese university students in April 2019 showed that over 65% of respondents know her. In addition, the pretest results also indicated that using celebrity endorsement in promoting pro-environmental behaviors is crucial (see appendix 2). We conducted a second round pre-test with a special focus on students’ perceptions of Hoang Thuy’s suitability as an endorser for plastic pollution campaigns. The results support our choices of celebrity endorser for this study. Over 80% respondents heard about Hoang Thuy (heard_of_HT) and 44% were aware of her engagement in environmental protection movement (HT_cleanup). Sixty percent respondents expressed positive view of her being able to inspire young people, while only 4% holds negative views (HT_inspire). Finally, 71% of respondents were positive about her being a suitable endorser for combating plastic pollution and only one respondent held a negative view on this (HT_plastic). Furthermore, respondents consider celebrity’s knowledge and experience as the most important aspect when judging the suitability of celebrity endorsers. Miss Hoang Thuy’s personal engagement in the effort to reduce plastic pollution fits this criterion perfectly. Based on the two round of pre-tests, we believe that Miss Hoang Thuy is an appropriate choice of celebrity endorser for this study.
We expect to capture the behavior changes as major outcome variables in natural field settings in several ways. First, we observe participants’ consumption of single-use plastic in a natural shop setting. We pay all participants , from both control and treatment groups, in our study with vouchers and they exchange the vouchers with a set of goods at the designated shops in the campus/students village. The set of the goods are things that commonly consumed by students, including a pack of milk, a soda drink, a pen and a container of mint tablet candy. These items are selected after consulting with a group of students. We work with the shops so that the students can exchange this set of goods at their cashier counter. They can decide whether to take plastic straws and use plastic bags at the counter when they finish the exchange. We do not add anything in the exchange process that may remind the students of the content of our study.
This setting provides a natural shopping environment for the students, so we can observe unprompted decisions of the students. We have an assistant at each counter to check the student ids, deliver the goods and record the plastic use for each student. We train the assistants to record the plastics use by marking the received vouchers with obscure symbols so that the students will not notice we are recording their plastic consumption. This setting will be repeated after baseline survey, after the workshops and after the endline survey. The vouchers are framed as compensation for participation in each stage of the study. The vouchers are only valid for five days and they are not transferable. Shops are chosen among the shop systems right at the or in close vicinity of the dormitory buildings to facilitate the exchanges. We expected that majority of the sampled students will come to the shop to exchange the voucher right after the voucher is handled. The key outcome variable is how many single use plastic items (i.e. straws and bags) a student use in each exchange. As well, we can also measure the time difference between the time point when the voucher is handled, and the time point when it is redeemed.
Second, we observe students’ voluntary participation in marine litter clean-up operations. We organize a trash clean-up event with the direct the help of the EfD Vietnam policy outreach and communication team sometime after the endline survey. We contact all the participants and invite them to join in the clean event in the vicinity (beach, lake or river side, a park). We use their signing-up decisions as a measure of real-life willingness to mitigate MPP problem.
Changes in KAPs regarding general environmental issues and PEB are the outcomes for potential spillover effects to PEB in other domains. Similar to measuring KAPs regarding plastic pollution, we measure awareness, knowledge and attitudes regarding other environmental issues with self-reported surveys questions. Beside the survey questions, we also measure pro-environmental behavior with an experiment. Specifically, we use a variation of a dictator game to measure individual’s willingness to contribute to an environmental NGO that does not focus on plastic pollutions. Every participant who finishes all stages of this study is entitled to a certain amount of money (i.e., 110 thousand VND ), as a bonus payment for the completing our study. Before delivering the money, we offer students an option to donate money out of the bonus payment to an environmental NGO. They can choose to donate any amount between 0 to 110 thousand VND and keep the rest to themselves. We will transfer the donations to the environmental NGO under the names of the individual students. We use the amounts donated to the NGO as a measure of the spillover effects on pro-environmental behavioral beyond the plastics pollution.
The randomly selected roommates of the workshop participants are also invited to the follow-up online survey. The purpose of this survey is to investigate the spillover effect to the participants’ peers, i.e., the spread of knowledge. We offer some lucky gifts that randomly drawing about 5% of the follow-up survey participants may receive a lucky gift and record their post-intervention consumption choices.