Sample Size
The sample size of 2766 was calculated to obtain an estimate of the expected 30% relative reduction in antibiotic prescriptions in the intervention arm compared with the control arm. The sample size calculation was based on a 55% expected antibiotic prescription rate in the control arm, with 80% power and a significance level of 5%. Sample sizes were optimized at a margin of precision of 4% with 15% loss to follow-up rate.