DePaul 1989.

Methods	Study design: Cluster‐randomized controlled trial Country: USA Recruitment: Employees at 38 worksites, recruited prior to a 3‐wk television smoking cessation programme
Participants	419 smokers who participated in the worksite programmes; 63% women in groups, 54% women in S‐H, av. age 38, av. cpd 21
Interventions	1. 6 x twice‐weekly group meetings to coincide with the 3‐wk television series, then monthly meetings for 1 yr. Abstinent smokers and 5 of their family and 5 co‐workers entered for a lottery at the final group meeting and 12 m follow‐up 2. S‐H manuals only
Outcomes	Abstinence from end of programme to 12 m Validation; saliva cotinine and co‐worker or relative confirmation
Notes	Data based on participants in the programmes. Attrition was defined as not attending any group meetings, not reading the manual, not being located for post‐testing, refusing to be interviewed or changing jobs. The attrition rate was 17% for group worksites and 29% for non‐group worksite participants, so correcting the data for attrition would increase the apparent efficacy of the group condition
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Cluster‐randomization by worksite, matched for size
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation of abstinence
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition rates reported, only those followed up used in MA, see Notes