The impact of personalized information on individual decisions to mitigate forever chemicals: Evidence from an online randomized evaluation

This study conducts an information intervention using an online survey to measure the causal impact of personalized information on people's averting behavior, measured as the individuals' water filter uptake to protect themselves against PFAS pollution of drinking water at home. PFAS information changes from no information for the control group to generic information for treatment 1 and personalized information for treatment 2. Following this intervention, the survey introduces three PFAS-removing water filters already available in the market. It asks participants about their interest in purchasing a certified water filter on a scale of 1 to 10. After that, the survey requests them to upload proof of purchase if they bought a PFAS-removing water filter.

The experiment is conducted in two rounds, and participants are compensated after they complete each survey.

To measure the causal impact of personalized information and address challenges in acquiring relevant details about the benefits and costs of aversion behaviors, we will conduct an online randomized experiment to examine the impact of personalized information on water filter purchase decisions. These filters are certified to remove PFAS. We plan to recruit 1,500 participants from a nationally representative sample and an additional 300 participants from Rhode Island, Delaware, and Maine for supplementary analysis. Participants will complete an online survey using the Prolific platform. The survey will assess participants' current behavior and preferences regarding tap water usage at home, their knowledge about PFAS, and their adoption of water filters as a PFAS-averting device.

The intervention will provide PFAS-related information based on random assignment to one of three groups: control, treatment 1, or treatment 2. The control group will receive minimal information, with participants only seeing what the acronym "PFAS" stands for. Treatment 1 will include generic information, such as what PFAS are, where they are found, and current regulations. Treatment 2 will combine this generic information with personalized details, tailored based on earlier survey responses about household composition and history of PFAS-sensitive diseases.

After the intervention, participants will be asked if they are willing to pay a randomly assigned amount between $10 and $250 for a certified water filter. They will then be introduced to three PFAS-certified water filters currently available on the market and asked to select their preferred product. Participants will rate their interest in purchasing a certified water filter on a scale from 1 to 10 and will also be asked whether they wish to purchase their selected product immediately. If participants choose to buy a product, the survey will provide a link to Amazon to facilitate the purchase and allow them to submit proof of purchase. Participants may also submit proof of purchase for any other certified water filter from any vendor. Participants retain the option to opt out and not purchase any device, in which case they will be asked to provide reasons for their decision.

To encourage participation, those who submit proof of purchase will be entered into a raffle at the end of the data collection period. Three winners will be randomly selected from the eligible pool and awarded $30 each, directly credited to their Prolific accounts.

Participants will receive compensation after completing each survey. If eligible, they may be contacted a maximum of twice during the study period. The first wave will include the main survey, which identifies participants who already own a PFAS-certified water filter and those who do not. The second wave will involve a follow-up survey (a shorter version of the main survey). Eligibility for the follow-up survey will be limited to participants who did not have a PFAS-certified water filter during the first wave, excluding those who submitted proof of purchase. The second-wave survey will deliver the same information as the first and ask participants if they sought additional information about PFAS and water filters between survey waves.

2025-02-24

2025-03-23

Submitting proof of purchase.

Submission of proof of purchase: Participants can upload proof of purchase of their preferred PFAS-removing water filter.

Level of interest in purchasing a water filter and willingness to pay (WTP) for a water filter certified to remove PFAS.

Level of interest in purchasing a water filter: Participants are asked to rate their interest in purchasing their preferred product among the options the survey introduced previously. The scale ranges from 1 (No interested at all) to 10 (Extremely interested).

WTP for a water filter certified to remove PFAS: The survey shows random integer values between $10 and $250 and asks participants whether they are willing to pay that amount to buy a water filter certified to remove PFAS.

Secondary measurements of interest: We track whether participants click on external links containing additional information on the water filter models we introduce in the survey.

We construct demographic groups based on whether there is a pregnant woman, children at or under the age of 13, and individuals suffering from PFAS-related diseases in the household. Individuals in each demographic group will be randomly assigned to the control or treatment groups in equal proportions.

The survey categorizes participants into two groups: Those with a water filter that removes PFAS and those without. Within each group, we create eight demographic categories based on the presence of a pregnant woman, children aged 13 or under, and individuals in the household suffering from PFAS-related diseases. Participants with a PFAS-removing water filter are randomly divided into two treatment groups (treatment 1 and treatment 2) with equal distribution unless they do not fall into any of the three demographic categories, in which case they are assigned to treatment 1. Participants without a PFAS-removing water filter are randomly allocated to the control group and treatment groups 1 and 2 in equal proportions unless they do not fall into any of the three demographic categories, in which case they are assigned equally to the control group and treatment groups.

We set up the randomization using the survey flow in Qualtrics.

This study randomly allocates participants to the control and treatment groups within each of the eight demographic categories based on the presence of a pregnant woman, children aged 13 or under, and individuals in the household suffering from PFAS-related diseases.

Yes

Eight

Pretest: 300 participants. Nationally representative sample:1,500 participants. Additional samples: 350 participants.

Since we lack prior information on the number of individuals living in households with children aged 13 or younger, pregnant women, or people with PFAS-related diseases, we cannot pre-estimate the distribution of participants across the control and treatment groups. However, the survey collects data on these characteristics to categorize participants into eight demographic groups. These groups will then be distributed equally and randomly among the control and treatment groups.

The study’s sample size is 2,000 subjects, determined by available funding. Based on a power calculation for a two-tailed test at a 0.05 significance level, with a power of 0.8 and an average proportion of 0.667 (using pretest data for the main outcome variable: whether a participant submitted proof of purchase), the minimum required sample size is 1,786 for an effect size of 1.85%. Additionally, the survey included questions about participants' intent to purchase. Based on data from the first round of the survey, the minimum required sample size for this variable is 965 subjects for an effect size of 7.7%.