We are collaborating with cantonal Departments of Education in Switzerland. In three cantons, we have access to the contact information of female staff aged between 25 and 50 in cantonal employment contracts, including kindergarten, primary, and secondary school teachers, for the school year 2022/23. We invite teachers to our study by email (if available) and by letter (all).
We conduct an individual-level randomization of teachers into the treatment and control groups. Due to the potential presence of spillovers between teachers working in the same school, we add a hold-out control group to this design. For the largest canton (in the following: Canton 1), we thus implement a two-stage randomization in the following way:
1. In the first stage, we randomize 2/3 of the schools into treatment schools and 1/3 into control schools (from now on referred to as the “pure control group”). We stratify the sample by terciles of school size (proxied by the number of female teachers aged 25-50 years working in each school based on the Department of Education contact list), school type (primary or secondary), and type of municipality (rural, semi-urban, city).
2. In the second stage, we randomize teachers in treatment schools at the individual level to treatment or control when participating in the survey. The individual-level randomization occurs during the survey, just before the intervention video starts playing. We assign ½ of the teachers to treatment and the rest to control.
For the rest of the cantons, we only randomize at the individual level (i.e., only the second step) and stratify by canton. Within the control group (both for the pure control and for the control), we randomize three control videos with equal probability. Our main focus for the analysis is the individual-level randomization of teachers into the treatment and control groups.