The population frame is constituted by  adolescents aged 12 to 17 years enrolled in schools of the 273 municipalities with 100,000 inhabitants in Brazil.

The sample will have regional and national representation.

1251 schools have been randomly selected in 124 municipalities, and a list of classes and students in eligible grades (7, 8 and 9 years of elementary school and 1st, 2nd and 3rd year of high school), will be prepared to allow random selection of three classes per school.

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