Evaluation of interventions to prevent injuries: an overview.

Overview of issues involved in evaluating the effectiveness of injury interventions is presented. An intervention should be evaluated to show it prevents injuries in the target population, to identify unintended consequences, to correct problems that limit effectiveness, to justify current and future resources from funding agencies, and to guide its replication elsewhere. Problems in conducting evaluations include obtaining sufficient resources, coping with rare events, establishing reliability and validity of measurement instruments, separating effects of multiple simultaneous events, and adjusting for the time lag between an intervention and its effects. When feasible, changes in injury rates (documented by medical records) should be used. These are more convincing for demonstrating intervention effectiveness than changes in observed or reported behaviors or in knowledge and attitudes (documented by surveys). Quasiexperimental evaluation designs are often useful, such as measuring injury rates before and after an intervention in a time series design, or intervening in one of two comparable communities in a nonequivalent control group design. Evaluations using true experimental designs, in which individuals or groups are randomized to receive or not receive an intervention, are highly desirable but are often difficult due to logistical or ethical considerations. An evaluation component should be integral to the introduction of any new injury intervention.