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ICCS 2009 Technical Report - IEA

ICCS 2009 Technical Report - IEA

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SummaryWhen student or teacher response rates within a school are very low, the likelihood of biasedresults increases. Therefore, minimum student and teacher participation rates within each schoolwere defined for <strong>ICCS</strong>.Several sets of weights were computed for <strong>ICCS</strong> data. These weights reflect varying selectionprobabilities for the selected students and teachers as well as varying patterns of nonparticipationbetween strata. All findings presented in <strong>ICCS</strong> reports are based on weighteddata, and any secondary analysis should be undertaken likewise.Unweighted and weighted response rates were calculated for the student and the teachersurveys. In order to inform readers of the <strong>ICCS</strong> reports about the quality of sampleimplementation, national student and teacher samples were assigned to different categoriesthat were determined according to the extent to which the samples had met <strong>ICCS</strong> sampleReference<strong>IEA</strong> Data Processing and Research Center. (2008). Windows ® within-school sampling software(WinW3S) [computer software]. Hamburg, Germany: Author.SAMPLING WEIGHTS AND PARTICIPATION RATES87

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