## Table 2 |
||||

Minimal effect size that can be detected for the revised sample size given comparison
arm risk behaviour prevalence, for a range of ICCs* |
||||

Effect size |
||||

Risk behaviours |
Control[7] |
ICC = 0.01 |
ICC = 0.04 |
ICC = 0.07 |

Alcohol use | 41% | 11% | 13% | 15% |

Substance abuse | 38% | 11% | 13% | 15% |

Tobacco use | 24% | 9% | 10% | 12% |

ICC = Intracluster Correlation Coefficient; Control = comparison arm.

*Calculations assume an 80% power with alpha of 5% for a two-sided test.

Sanci * et al.*

Sanci * et al.* *BMC Public Health* 2012 **12**:400 doi:10.1186/1471-2458-12-400