The effectiveness of air bags

Previous research has shown that the installation of air bags in vehicles significantly reduces crash related deaths, but these analyses have used statistical techniques which have not been capable of controlling for other major determinants of crash survival. This study analysed data from the US FARS database of fatal crashes using conditional logistic regression which is simultaneously able to estimate occupant protection effects for a range of variables. Results of the analysis provided a comparative quantification of both the effect of the air bag as well as other well known determinants of occupant crash survival (age, seat belt use, and gender). When potentially confounding variables were controlled, both the driver and passenger side air bag devices were shown to significantly reduce the probability of death in direct frontal collisions, but the effect size calculated was small compared to the effect of the seat belt. The effect size may also be very small in absolute terms depending on the severity of the crash involved. Given the limited benefit of the air bag, efforts to promote air bags seem particularly difficult to justify in countries such as the United States where the vastly superior occupant protection of the seat belt is under-utilised

Predicting change in smoking status for self-changers

Fourteen different measures were investigated as predictors of change in smoking status for self-change efforts at smoking cessation. Adult subjects (N = 866) were classified into five stages of change: precontemplation, contemplation, action, maintenance, and relapse. Subjects were assessed on 10 change processes, self-efficacy, temptations to smoke, and their decisions weighing the advantages and disadvantages of smoking; and these 14 variables were used as predictors of change in smoking status 6 months later. Six significant functions were found which predicted movement for each of the stages. These predictors are both theoretical interest and practical significance because they may be modified in self-change efforts to overcome addictive behaviors. Overall, the change processes of self-reevaluation and the helping relationship and the self-efficacy and decisional balance variables were the most efficacious predictor variables. A general pattern emerged in which processes oriented more toward environmental events, such as dramatic relief and social liberation, tended to predict failure or no progress whereas more experientially oriented processes predicted progress. © 1985