Are you currently a smoker?
(For smokers only) In the last year, how many times have you quit smoking for at least 24 hours?
(For smokers only) Are you seriously thinking of quitting smoking?
DiClemente, C.C., Prochaska, J.O., Fairhurst, S., Velicer, W.F., Rossi J.S., & Velasquez, M. (1991). The process of smoking cessation: An analysis of precontemplation, contemplation and contemplation/action. Journal of Consulting and Clinical Psychology, 59, 295-304.
Velicer, W.F., Fava, J.L., Prochaska, J.O., Abrams, D.B., Emmons, K.M., & Pierce, J. (1995). Distribution of smokers by stage in three representative samples. Preventive Medicine, 24, 401-411.