Omenn 1988.

Methods	Study design: Randomized controlled trial Country: USA Recruitment: Single worksite (13,000 workers, 9 employers) Group size: typically 15 ‐ 20
Participants	159 smokers; 66% men, av. age 43, av. cpd 25, with preference for group programme or no preference (Smokers with preference for S‐H were not allocated to group programmes) Led by instructors trained in both programmes
Interventions	1. Multiple Component programme. 3 sessions over 3 wks. Didactic format 2. RP programme. 8 sessions over 8 wks. Interactive format, choice of immediate or phased quit 3. Minimal Treatment programme. S‐H materials only. ACS 22‐page Quitter's Guide 7‐day plan
Outcomes	Abstinence at 12 m (single PPA) Validation: saliva cotinine ≤ 35 ng/ml
Notes	1+2 vs 3 in comparison 1.1.2 vs different S‐H. No difference in outcome at 12 m between 2 group programmes. Self‐reported quit rates similar across all 3 conditions but more missing saliva samples in S‐H so validated rates lower
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"nurses at aid stations using randomized assignment lists generated by research centre, within preference for format"
Allocation concealment (selection bias)	High risk	Mention of lists and not envelopes suggests that concealment unlikely
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation of abstinence
Incomplete outcome data (attrition bias) All outcomes	Low risk	At least 89% followed up in each arm