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Table 2 Number of participants and clusters required in a multilevel study

From: Study protocol of an RCT of EMOTION: An indicated intervention for children with symptoms of anxiety and depression

Estimated ICC

Calculated DEFF

Number of children

Number of schools

0.00 - Base model

1

260

15

0.05 - Two-level model

2.15

559

23(36)a

  1. ICC the intraclass correlation coefficient, n number of pupils, DEFF design effect = 1 + (nc - l)*ICC, (nc average number of individuals in a school = 24); The first value (260) is from Altman [26], page 456, and the next figures are multiplied with the calculated DEFF value
  2. aThe first number denotes the required sample size given the power calculation. The parenthetical number denotes the actual number of schools recruited for the study based on other practical considerations
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BMC Psychology

ISSN: 2050-7283

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