Elder 1993.

Methods	Country: USA Site: 22 junior high schools in San Diego County, CA (11 to intervention, 11 to control). 'SHOUT' Students Helping Others Understand Tobacco. Focus: Tobacco use prevention. Design: Cluster RCT (Group 3: point prevalence).
Participants	Baseline: 3655. Cohort of 2668, 73% of initial sample, 1174 in Experimental, 1494 in Control. Age: mean 12 yrs (range 11 ‐ 16). Gender: "near equal proportions of M and F" Ethnicity: overall ‐ 57% W/non‐H, 24% H, 19% Other. Baseline smoking data: Smoking rates: beginning 7th grade Intervention 5% control 5.6%.
Interventions	Category: Social influences vs control. Programme deliverer: undergraduates (received 15 hrs of training including videotaped role plays). Intervention: 7th grade: Fall: (6 lessons, 1 a week) videos of health consequences of tobacco use, celebrity endorsements of non‐use, psychosocial consequences, refusal skills, decision‐making, skits; Spring: (4 lessons, 1 a month) review of refusal methods, discussion of tobacco addiction/cessation, public declarations of non‐use and skits; 8th grade (8 lessons, 1 a month): demonstration/rehearsal of refusal skills, writing campaigns against tobacco use, community action projects, discussion groups and debates. 9th grade (booster intervention) ‐ 5 newsletters containing tobacco control events, legislation, research and tobacco industry's power, cessation tips, 2 newsletters mailed to SHOUT participants' parents and phone calls (2 per semester) following Pawtucket Heart Health Programme protocol oriented toward newsletter material, refusal skills training and cessation support (79.9% call completion rate). Control: No interventions.
Outcomes	Smoking: Any tobacco use (cigarettes and smokeless) in past month and past week. Self report surveys under 'bogus pipeline' conditions. Follow up: End of 7th, end of 8th, end of 9th grades.
Notes	Elder 1993a and 1993b discrepant on number of sessions/year. See also Eckhardt 1997 which provided further intervention to the cohort. Quality of intervention delivery: No process analysis, but the 100 undergraduate volunteers were closely supervised, received academic credit, 15 hrs of training included videotaped role plays, and "attrition was rare". "Training included how to teach effectively and how to implement SHOUT lessons. The leader's role plays were videotaped and reviewed. Proficiency was evaluated by staff, and feedback was given during training and later in the field". Statistical quality: Was a power computation performed? No. Was an intention‐to‐treat analysis performed? Not stated. Was a correction for clustering made? Not stated. Were appropriate statistical methods used? LR and logit model ORs.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"An initial sample of 22 schools with 3655 participants was identified in fall 1988. This sample was matched by tobacco use prevalence (in past week) and school size, and randomly assigned to either a control or an intervention condition". Clusters: Schools Cluster constraint: Schools matched by tobacco prevalence use and school size. Baseline comparability: Ethnicity showed significant group differences (P < 0.001).
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	Pretest: 3655. Cohort of 2668 (73% of initial sample). No differential attrition.
Selective reporting (reporting bias)	Low risk	No selective reporting.