Table 1.

Predictors of the number of different days when the app was accessed, ranked in decreasing order of importance

Predictors	%IncMSE
Intention to quit smoking assessed at 1-month follow-up	47.21
Cigarettes/day measured at 1-month follow-up	38.78
Perceived helpfulness of the app measured after 1 month	22.88
Having quit smoking after 1 month	17.47
Experiment group (treatment vs. control)	15.45
Age	8.94
Number of years smoking	7.65
Current use of any smoking cessation app, as self-reported at 1-month follow-up	5.68
Cigarettes/day as measured at baseline	5.09
Use of e-cigarettes at baseline	4.56
Use of heated tobacco product as self-reported after 1-month follow-up	4.03
Number of minutes before the first cigarette of the day	3.42
Use of nicotine medications after 1-month follow-up	2.85
Use of e-cigarettes after 1-month follow-up	2.01
Use of nicotine medications at baseline	1.71
Depression screening test positive	1.22
Use/smoke other tobacco products at baseline	1.14
Country (Switzerland vs. France)	0.81
Use of heated tobacco product at baseline	0.58
Sex	0.48

%IncMSE, percent increase in mean squared error, a statistical measure indicating the level on the predictor variable importance in the regression machine learning algorithm.