title: "Imagine a can opener"--the magic of principal stratum analysis.
abstract: Abstract     We extend Pearl's criticisms of principal stratification analysis as a method for interpreting and adjusting for intermediate variables in a causal analysis.  We argue that this can be meaningful only in those rare cases that involve strong functional dependence, and even then may not be appropriate.
authors: University of Cambridge, UK.
authors: Philip
authors: P
authors: Dawid
authors: Vanessa
authors: V
authors: Didelez
mesh_terms: D015984:Causality; D003627:Data Interpretation, Statistical; D006801:Humans; D057182:Mendelian Randomization Analysis; D015233:Models, Statistical