Sample size (or number of clusters) by treatment arms
Wave 1: second year of high school
Control group = 739 students, 13 schools
Treatment group 1 = 408 students, 12 schools
Treatment group 2a = 481 students, 10 schools
Wave 2: third year of high school
Control group = 111 students, 5 schools
Treatment group 1 = 91 students, 4 schools
Treatment group 2b = 119 students, 4 schools
Total sample
Control group = 850 students, 18 schools
Treatment group 1 = 499 students, 16 schools
Treatment group 2 = 600 students, 14 schools
Average number of schools per condition = 16
Average number of students per condition = 649.7
Average number of students per school = 40.6
Please note that as teacher characteristics were included as control variables in the final analyses, this resulted in missing values for a selection of students. Consequently, the final sample reported in the article is somewhat smaller:
Wave 1: second year of high school
Control group = 675 students, 13 schools
Treatment group 1 = 401 students, 11 schools
Treatment group 2a = 481 students, 10 schools
Wave 2: third year of high school
Control group = 111 students, 5 schools
Treatment group 1 = 91 students, 4 schools
Treatment group 2b = 86 students, 3 schools
Total sample
Control group = 786 students, 18 schools
Treatment group 1 = 492 students, 15 schools
Treatment group 2 = 567 students, 13 schools