2.3. Sample Size and Early Termination Plan
The target sample size for BENIT was 324, which was based on a difference of 13 percentage points between intervention and control for ANBQ chewing cessation prevalence at 22 days with α = 0.05 (2-sided) and β = 0.20. However, an early termination plan was developed to accommodate the possibility of stronger-than-expected intervention effects. The specific plan employed the O’Brien-Fleming procedure for interim analysis to maintain the nominal type I error probability of 0.05. This procedure has been described previously [