DePaul 1987.

Methods	Study design: Cluster‐randomized controlled trial Country: USA Recruitment: Employees at 43 worksites, recruited prior to a 3‐wk television smoking cessation programme
Participants	233 smokers in group discussion worksites, 192 in non‐group worksites; 72% women, av. age 43, av. cpd 30 Groups led by employee with 3 hrs training
Interventions	All participants were given S‐H manuals by company co‐ordinators and instructed to view the televised segments 1. Twice‐weekly 45‐min group meetings for 3 wks 2. S‐H alone
Outcomes	Abstinence at 12 m (multiple PPA) No validation
Notes	Percentage quit rates estimated from graphs and denominator assumed to be numbers followed‐up
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Cluster‐randomization by worksite, matched for size. 3 worksites did not enter allocated condition but excluding them did not alter findings
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding of outcome assessment (detection bias) All outcomes	High risk	No validation of abstinence
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	8% lost to follow‐up in each group