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in two-stage cluster sampling, a random sampling technique is applied to the elements from each of the selected clusters...
die elemente der klumpen werden dann allerdings vollständig erfasst (alle schüler der ausgewählten schulen werden befragt).
they were selected using a cluster-random sampling method and were randomly assigned to the intervention (n=40) and control groups (n=40).
they were selected using a cluster-random sampling method and were randomly assigned to the intervention (n=40) and control groups (n=40).