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Number of participants and clusters required in a multilevel study
| Assumed ICC | Design effect | N indiv | n/cluster | N schools | |
|---|---|---|---|---|---|
| A | 0.00 – Base model | 1 | 400 | 20 | 20 |
| B | 0.05 – Two-level model | 1.95 | 800 | 20 | 40 |
Design effect = 1 + (nc − 1)
ICC intraclass correlation coefficient, n number of pupils
*ICC (nc = average number of individuals in a cluster = 20)
