Other measures
Participants answered questions in an on‐line questionnaire at the end of each intervention period to report any mitigating factors that they felt had affected their smoking in the preceding 2 weeks (see Supporting information, Material Participants answered questions at the end of the study in an on‐line questionnaire covering their purchasing of cigarettes during each intervention period; that is, whether they bought cigarettes in single packs, multiple packs or cartons), reasons for pack size preferences and what they thought the study was about (see Supporting information, Material 