Sample Size
As this was a pilot RCT and the first assessment of Pivot compared with usual care, the sample size was powered to show differences in engagement, specifically, the number of times participants opened their assigned app over the first 12 weeks of the study. The methodology to power the study for engagement and the associated outcomes have been previously reported. Pivot participants self-reported a mean of 157.9 (SD 210.6) total app openings versus 86.5 (SD 66.3) in the QuitGuide group (incidence rate ratio [IRR]=1.8, 95% CI 1.4-2.3; 