Wright 1995.

Methods	CBA
Participants	Participants were boys and girls aged 11 and 15 years (3 middle schools and 3 high schools) from state schools in the US, located in rural, urban and suburban settings. Number of participants: 663 (372 middle school and 249 high school) in the intervention group and 78 children in the control group.
Interventions	Intervention: Think First programme. Intervention was delivered by Think First project staff and a victim of injury. Children were presented with a short film, were given a lecture and a talk by a victim of a traumatic brain or spinal cord injury, which was followed by a question and answer session. The focus of the talks was on action regarding seat‐belt use, use of motorcycle helmets, cycle helmets, as well as the avoidance of drugs and alcohol while driving or participating in sports. Also included was the importance of checking for the depth of water when swimming or diving. Control: received the same intervention, although delayed until after data collection.
Outcomes	Observed behaviour (seat belt and helmet wearing on leaving school). Self‐reported behaviour and practices assessed by questionnaire. Safety knowledge assessed by questionnaire. All outcomes were measured at 2 weeks' and 3 months' post‐intervention.
Injury mechanisms	Pedestrian, cycle, motorcycle, vehicle (non‐specific)
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation to intervention/control (selection bias) (for non‐RCT and CBA studies)	High risk	Intervention schools were a convenience sample. In addition, the baseline characteristics of the 2 groups were different ‐ participants in the control group were older.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and people delivering the intervention not blinded.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Students aware of group allocations when they completed the questionnaires. Not reported whether people assessing the behaviour outcomes were blinded to the group allocations.
Incomplete outcome data (attrition bias) All outcomes	High risk	High attrition at 3 months in the intervention group. Only 37.4% of the total number of children allocated to the intervention group at baseline were followed up.
Selective reporting (reporting bias)	High risk	For behavioural outcomes, only selected items reported.
Other bias	High risk	Control group used a shortened questionnaire.
Risk of bias due to confounding (for non‐RCTs and CBA studies)	High risk	Control and intervention groups not matched, no adjustment for confounding mentioned.