Guyer 1989.

Methods	CBA (C) Allocation at level of cities and towns
Participants	Population of 14 cities and towns in Massachusetts
Interventions	I = Community injury prevention programme including injury counselling by paediatricians to parents of young children, school and community burn prevention education, home safety inspections + community wide promotion of poison centre service C = no community injury prevention programme
Outcomes	Outcomes measured over 22 months: Rate of medically attended poisonings ‐ poisoning rate I = 36.14/10,000 person years C = 92.71/10,000 person years, OR 0.95 (0.57 to 1.58) (adjusted for socio‐economic group) Rate of medically attended fall injuries ‐ I = 175.02/10,000 person years C = 262.44/10,000 person years OR 0.78 (0.61 to 1.00) (adjusted for socio‐economic group) Medically attended thermal injuries ‐ I = 59.68/10000 person years C = 106.03/10000 person years OR 1.26 (0.84 to 1.90) (adjusted for socio‐economic group) Possession of smoke alarm Preventive behaviour score comprising behaviours for preventing poisonings (14 items), burns (12 items), falls (6 items) ‐ Mean score: Burns: I = 49.2, C = 46.8 Falls I = 30.3, C = 30.7 Poisoning I =34.3, C = 30.5. P values not reported
Notes	Blinding ‐ u Outcomes 80% ‐ y Balance ‐ n Control communities had higher baseline injury rates, a greater proportion of Hispanic residents and lower household income than intervention communities
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	Not applicable ‐ non‐randomised study