title: Response to Pearl's comments on principal stratification.
abstract: Dr. Pearl invites researchers to justify their use of principal stratification. This comment explains how the use of principal stratification simplified a complex mediational problem encountered when evaluating a smoking cessation intervention's effect on reducing smoking withdrawal symptoms.
authors.affiliation: Fox Chase Cancer Center.
authors.forename: Brian L
authors.initials: BL
authors.lastname: Egleston
mesh_terms: D015984:Causality; D006801:Humans; D015233:Models, Statistical; D016032:Randomized Controlled Trials as Topic; D012107:Research Design