3. Empirical methods
3.1. Data
3.1.1. Identifying lung cancer patients
We started with 1853 male lung cancer patients diagnosed during
May–October 2011 in a large city in China. Hospital-based
health care professionals contacted these men by telephone (or
relatives if they were too ill to respond or had died) and asked: (1)
if the man ever smoked and if yes, the number of years he smoked;