Randomization
RECRUITMENT
We randomized participants using a table conducted in random blocks of different sizes (8 and 12 participants) to ensure balance among groups and reduce predictability of the allocation process. Randomization occurred in 2 stages at the time of initial registration. Participants were first randomized to receive messages from the ML recommender or standard messaging communication systems. This was followed by an allocation to receive or not receive access to the viral tool kit depending on the recruitment source captured via a self-report question presented to participants immediately after they consented to the study. The question was “How did you hear about Decide2Quit?” and answer choices included a friend or family member, online ad (Facebook or Google), ResearchMatch, or the SmokeFree government site. All peer-recruited participants (those who indicated that they were referred by friends or family) received access to the viral tool kit to reduce cross-contamination given that these peer-recruited participants could communicate with their peers about the viral tool kit. Participants who indicated other sources were randomly allocated to receive or not receive the viral tool kit. Study staff were blinded to allocation during initial baseline assessment and follow-up.