Sampling
Sampling Procedure
The sample is drawn using a three-stage stratified sampling design. The schools are divided in six strata based on the type of schools (regular schools (public, private and community) and schools that underwent a curriculum reform in 2008 (public, private and community schools in 20 school districts out of 111), the type of classroom (regular and multigrade) and the class schedule (half time and full time)
In the first stage, a random sample of 165 schools was selected using probability proportional to size.
In the second stage, a random sample of classrooms is selected using simple random sampling.
In the third stage, a random sample of 15 students for each selected classroom is selected using simple random sampling.
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