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Last Published October 18, 2019 10:52 AM December 06, 2019 03:36 PM
Intervention (Public) In this RCT we exploit the naturally occurring exogenous variation in air pollution as our treatment intervention. Participants will be randomly assigned to either a low pollution control group or a high pollution treatment group. Using the official Air Quality Index (AQI) classifications as a broad guideline, we define low levels of air pollution for AQI values in the ‘Good’ to ‘Unhealthy for Sensitive Groups’ range and high levels of air pollution for AQI values exceeding ‘Very Unhealthy’ levels of pollution. As pollution episodes generally occur over a series of days, preceded and followed by clean day-time episodes, participants from both treatment and control groups will be surveyed within a timeframe of several weeks. Pollution and weather forecasts will be used to determine the exact distribution date of the experimental survey. 1) Participants in the low pollution control group will be invited to complete a set of incentivised tasks when air pollution levels are objectively low, preceding a forecasted pollution episode. 2) Participants in the high pollution treatment group will be invited to complete the same set of incentivised tasks at the peak of the pollution episode. Absolute levels of pollution exposure may vary and AQI classifications will serve as a guideline only; however, we aim to choose those days with the largest standard deviation between low and high pollution groups within each sampling period, subject to pollution and weather forecasts. To verify that official pollution levels are precise, we will take additional air quality measurements using modern air pollution measuring equipment located on the Campus of Renmin University. In this RCT we exploit the naturally occurring exogenous variation in air pollution as our treatment intervention. Pollution episodes generally occur over a series of days, followed by wind-driven clean-air episodes. By exploiting this natural discontinuity in air pollution exposure, we are able to survey both treatment and control groups within a timeframe of several days. Participants will be randomly assigned to one of four groups, a low pollution (control group) or one of three high pollution treatment groups. The three high pollution treatment groups differ with respect to the magnitude of air pollution and whether a pollution alert was issued by the research team prior to the survey distribution. All participants will be notified via direct messages about the upcoming survey, 24-hours prior to survey distribution. Pollution and weather forecasts will be used to determine the exact distribution date of the experimental survey. We utilise the official Air Quality Index (AQI) classifications as a broad guideline to define objective pollution levels for each treatment group: 1) Participants in the low pollution control group will be invited to complete a set of incentivised tasks when air pollution levels are objectively low, with AQI values in the ‘Good’ to ‘Unhealthy for Sensitive Groups’ range. They will be notified 24-hours in advance about the upcoming survey. 2) Participants in the high pollution treatment group will be invited to complete the same set of incentivised tasks when air pollution levels are objectively high, with AQI values exceeding ‘Very Unhealthy’ levels of pollution. They will be notified 24-hours in advance about the upcoming survey. 3) Participants in the high_alert pollution treatment group will be invited to complete the same set of incentivised tasks at the same time as group (2). They will be notified 24-hours in advance about the upcoming survey and receive an additional warning message about the expected unhealthy levels of air pollution. 4) Participants in the high_max pollution treatment groups will be incited complete the same set of incentivised tasks when air pollution levels are extremely high, with AQI values in the ‘Hazardous’ range. Absolute levels of pollution exposure may vary and AQI classifications will serve as a guideline only. To verify that official pollution levels are precise, we will take additional air quality measurements using modern air pollution measuring equipment located on the Campus of Renmin University.
Experimental Design (Public) The proposed RCT involves approximately 700 student participants enrolled at universities in Beijing, China. Data will be collected via online survey experiments using the Chinese messenger app 'WeChat'. Students will be contacted via direct messages and invited to participate in the study by following a link to an external survey platform. Once participants have completed the online survey, they will be immediately compensated via direct payment to their 'WeChat Wallets'. We will implement an online between-subject experimental design in which students will be randomly assigned to one of two high pollution treatment groups or one of two low pollution control groups, using a stratified randomisation procedure. The first treatment and control group will be sampled in October/November 2019. The second groups will be sampled in November/December 2019. Participants in the low pollution treatment conditions will be invited to complete the survey when air pollution levels are objectively low, preceding a forecasted pollution episode. Participants in the high treatment conditions will subsequently be sampled at the peak of the pollution episode. The exact sampling dates will be determined based on pollution and weather forecasts. The proposed RCT involves approximately 700 student participants enrolled at universities in Beijing, China. Data will be collected via online survey experiments using the Chinese messenger app 'WeChat'. Students will be contacted via direct messages and invited to participate in the study by following a link to an external survey platform. Once participants have completed the online survey, they will be immediately compensated via direct payment to their 'WeChat Wallets'. We will implement an online between-subject experimental design in which students will be randomly assigned to a low pollution control group or one of three high pollution treatment (high, high_alert, high_max), using a stratified randomisation procedure. All four groups will be sampled in December 2019. Participants will be notified 24-hours in advance about the upcoming survey via direct message. Participants in the high treatment condition will be sampled at the peak of a pollution episode. Participants in the high_alert treatment condition will be sampled at the same time but will have received an additional pollution alert with the survey notification (24-hours prior to the survey). Participants in the low pollution treatment conditions will be invited to complete the survey when air pollution levels are objectively low, immediately after the pollution episode. Participants in the high_max treatment condition will be sampled at the peak of a more extreme pollution episode. The exact sampling dates will be determined based on pollution and weather forecasts.
Sample size (or number of clusters) by treatment arms The sample will be equally split between treatment and control group. The treatment and control group will be split into two groups, sampled at different time-points throughout the semester. The sample will be equally split between all four groups.
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