The study Smoking and Health (Surgeon General, 1964).

• This study linked cigarette smoking with lung cancer by the simple methods of counting and correlating.
• There were definite relationships and associations between smoking and lung cancer (e.g., about 90% of lung cancer in males was associated with cigarette smoking, and the amount and duration of smoking were positively correlated with probability of cancer).
• It is true that epidemiological research frequently suggests the possibility of multiple causation (several factors must be present before the disease occurs, or the greater the number associated factors that are present, the greater the risk of the disease).