Final Sample Size (or Number of Clusters) by Treatment Arms
We use a 2 times 4 design to obtain eight experimental arms corresponding to different combinations of three cascading information nudges and one mask treatment. The mask treatment provides three free KN95-type anti-pollution facemasks (APFs) while the three cascading information nudges are designed in the form of a combination of an information brochure and three different versions of calendars. The information brochure contains detailed information about smog and PM pollution, the health effects of the smog, defensive measures taken on smog days such as reduced outdoor activities and mask-wearing, roles of APFs in reducing the health effects of smog, different brands of APFs available on the market, the difference between APFs and regular cotton facemasks, and proper ways of wearing APFs. On the V1 calendar, participants are asked to fill out their daily information regarding how many hours they stay outdoors (outdoor time) and how many hours they wear facemasks when being outdoors (mask-wearing time) on each day during the whole winter heating season (from November 2018 through March 2019). The V2 calendar builds on the V1 calendar but requires the participants to carry out two additional tasks, i.e. checking one of four boxes corresponding to four intervals of daily mean AQI (i.e. 0-100, 101-200, 201-300, and 301 and higher) and one of four boxes corresponding to the health impact of the air quality (i.e. no impact, some impact, big impact, and very big impact). The V3 calendar is like the V2 except that the V3 requires the participants to check an additional box among four boxes corresponding to the necessity of wearing an APF (i.e. no need, somewhat necessary, necessary, and very necessary).
The eight experimental arms are as follows: arm 1 provides calendar version 1, arm 2 provides calendar version 1 together with free masks, arm 3 provides a calendar version1 together with an information brochure, arm 4 provides calendar version 1, one information brochure and free masks, arm 5 provides calendar version 2 and one information brochure, arm 6 provides calendar version 2, one information brochure and free masks, arm 7 provides calendar version 3 and one information brochure, and arm 8 provides calendar version 3, one information brochure and free facemasks.
The eight experimental arms are randomly assigned to 40 neighborhoods. Half (20) of the neighborhoods (arms of 2, 4, 6, and 8) receive the mask treatment where each participant is given three free KN95-type APFs while another half (20) do not receive the APFs. Three-quarters (30) of the neighborhoods (arms of 3, 4, 5, 6, 7, and 8) receive three cascading information nudges: 10 neighborhoods (arms of 3 and 4) receive the passive information nudge, 10 neighborhoods (study arms 5 and 6) provided with the active pollution information nudge, and 10 neighborhoods (study arms 7 and 8) given the active APF information nudge. One quarter (10) of the neighborhoods (arms of 1 and 2) receive the V1 calendar but not the brochure; among them, five neighborhoods receive the APFs while the other five do not receive APFs. The control group is the neighborhoods only receiving the V1 calendar, but not the information brochure or free APFs.