Perceived effectiveness of stop smoking interventions: impact of presenting evidence using numbers, visual displays, and different timeframes.

INTRODUCTION: This study investigates the impact of visual and numerical representations of effectiveness and different lengths of follow-up upon the perceived effectiveness of stop smoking interventions.
METHODS: This study entails two between-subjects experiments with smokers from the general population. In Experiment 1, U.K. smokers (n = 318) viewed information about a stop smoking intervention that included (a) no effectiveness information, (b) standard numerical effectiveness information, or (c) numerical and visual absolute effectiveness information. In Experiment 2, U.K. smokers (n = 320) viewed numerical and visual absolute effectiveness information about a stop smoking intervention showing either the short-term (1-month) or the long-term (12-month) quit rate with and without intervention. Outcome measures included perceived effectiveness of stop smoking interventions and intentions to use them.
RESULTS: In Experiment 1, numerical and visual absolute effectiveness information compared with no effectiveness information resulted in greater perceived effectiveness (Scheffé test, p = .033, Cohen's d = 0.36) and intentions to use stop smoking interventions (Scheffé test, p = .012, d = 0.43). No differences were detected between standard numerical effectiveness information and no effectiveness information. In Experiment 2, the short-term quit rate compared with long-term quit rate resulted in greater perceived effectiveness, t(318) = 3.2, p = .002, d = 0.35, but not significantly greater intentions to use stop smoking interventions, t(318) = 1.59, p = .11, d = 0.18.
CONCLUSIONS: Presenting numerical and visual absolute effectiveness information about the short-term effectiveness of stop smoking interventions may increase the use of stop smoking interventions.