a. Case-control study (1950)
1,465 cases were diagnosed in 20 hospitals in London :
pairing of 1 case and 1 control (patients hospitalized for a non-cancerous pathology) according to gender and age.
data related to tobacco consumption, exposure to pollution, etc. was collected.
They concluded that cigarette smoking is the factor that is the most greatly tied to lung cancer. Even though this was the first study of its kind, it was subject to criticism as soon as it was released.