Statistical plan
REGRESSION
With an initial sample size of 600 Drivingly dyads and 600 controls assuming 10% dropout in each group, a 1-year post-licensure crash risk in the unexposed group of 15%, and significance level (α) of 0.05, we will have 90% power to detect a hazard ratio (HR) of 0.59 for the first year of licensure. Alternatively, assuming a first-year control group crash rate of 20% the detectable HR is 0.65 for the first year of licensure; assuming a 25% first-year crash rate, the detectable HR is 0.69 [Risk ratios comparing the risk of any MVC involvement between Drivingly and Control will be estimated using modified Poisson regression [To evaluate Drivingly’s conceptual model (Fig. If there is substantial item-level missingness in the survey data (e.g., in excess of 5%), we will assess whether non-response bias may be present; however, if we find such differences, we will use multiple imputation with chained equations as suggested by prior research under the relatively mild assumption of missingness at random [