ICCS 2009 Technical Report - IEA

Systematic sampling was used for selecting classes from lists provided by the participatingschools. This procedure was similar to the one used for systematic school sampling except thateach class in a school had the same probability of being selected. Each student in a participatingschool had the same selection probability because all students within sampled classes wereselected for participation in ICCS.Whenever a class was smaller than half of the average class size, it was grouped with one ormore other classes prior to sample selection to form a pseudo-class. This approach was used toavoid fluctuations in the total student sample size and to ensure efficient use of study resources.Teacher samplingWinW3S employed systematic sampling with equal selection probabilities to select teachersfrom lists provided by the participating schools. In order to ensure a proportional allocationof teachers by gender, the implicit stratification was applied when using WinW3S to sampleteachers.As mentioned above, it was possible to select specific groups of teachers with certainty.The sampling team accounted for the higher selection probabilities of these teachers whenconducting weight calculations.SummaryThe ICCS student target population consisted of students enrolled in the grade that representedeight years of schooling, providing that the students’ mean age at the time of testing was atleast 13.5 years. The teacher target population consisted of teachers teaching regular schoolsubjects to students of the target grade.National centers were allowed to exclude groups of students from the study for practicalreasons. However, each country was required to keep the overall rate of excluded studentsbelow five percent of the target population.As a default, ICCS required a minimum sample size of 150 schools, in which one intactclassroom and 15 teachers were selected for the study. The national samples were designed toyield a student sample size of roughly 3,000 tested students.The international sample design was a stratified two-stage probability sampling design. Schoolswere selected with PPS; classes and teachers within sampled schools were selected with equalselection probabilities.ReferencesIEA Data Processing and Research Center. (2008). Windows ® within-school sampling software(WinW3S) [computer software]. Hamburg, Germany: Author.Martin, M. O., Rust, K., & Adams, R. J. (1999). Technical standards for IEA studies. Amsterdam,the Netherlands: International Association for the Evaluation of Educational Achievement(IEA).UNESCO. (2006). International Standard Classification of Education: ISCED 1997. Montreal,Quebec, Canada: UNESCO Institute for Statistics.68ICCS 2009 technical report