Schinke 1988.

Methods	Country: USA. Site: 2 Indian reservations in western Washington state Focus: prevention of smoking, alcohol and drug use; assess the effects of a 10 session prevention programme. Design: cluster RCT (excluded from analysis)
Participants	Baseline: 137 Age: 11.8yrs Gender: 54% F Ethnicity: all Native Americans Baseline smoking data: no data
Interventions	Category: social influences vs. control Programme deliverer: Native American counsellors Intervention: 10 sessions; programme to learn bicultural competence skills taught by Native American counsellors. Communication, coping and discrimination skills, modelled, coached and praised turning down substance offers from peers without offence, taught self instruction and relaxation to help refuse offers of substances, rewarded refusals, anticipated temptations, predicted high‐risk situations, built networks with friends and family, homework supporting each others' refusals. Control: No programme
Outcomes	Definition of smoking: Self reported smoking in previous 14 days Follow up: 6m
Notes	Quality of intervention delivery: no process analysis Statistical quality: Was a power computation performed? No (n only 137) Was an intention‐to‐treat analysis performed? Not stated Was a correction for clustering made? No Were appropriate statistical methods used? Comparisons at baseline by by ANOVA, for intervention effects over time MANOVA, "When univariate ANOVAS showed significant condition differences, posttest and follow‐up data were analysed by Tukey‐Kramer procedures for paired comparisons...".
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"After pre‐testing, subjects were randomly divided by reservation site into prevention and control conditions." Method of randomisation not stated Clusters: reservations Cluster constraint: not stated Baseline comparability: experimental and control groups were similar at baseline.
Allocation concealment (selection bias)	Unclear risk	No statement
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No statement
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition 8% at 6m with no differential attrition between groups
Selective reporting (reporting bias)	Low risk	No selective reporting