Owen 1989.

Methods	Setting: community, Australia Recruitment: advertisements for smokers wishing to quit
Participants	208 smokers; average age 42, average cpd 28
Interventions	∙ Quit Kit along with apology that course was full. Kit included a 5‐day cessation plan ∙ Self‐help programme in 4 mailed parts ∙ As in second bullet above, but personalised with additional text based on registration form (option to send for additional materials)
Outcomes	Abstinence at 9 months (point prevalence) Validation: some cotinine assays but no correction for a possible 15% misreport level
Notes	First intervention listed above meets criteria for basic self‐help, so 2 vs 1 for effect of additional materials and 3 vs 2 for effect of personalised materials
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised; method not described
Allocation concealment (selection bias)	Unclear risk	No details given
Blinding (performance bias and detection bias) All outcomes	High risk	Control group (1) received notice that course was full; could introduce performance bias by artificially decreasing control group quit rates
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	12% lost to follow‐up at 9 months; similar between groups Non‐respondents included as smokers