A Case-Control Study Was Needed to Determine an Association Between

Multiple Choice

A case-control study was needed to determine an association between the exposure (tobacco) and outcome (lung disease) . If the control group (non-smokers) has the same incidences of lung cancer as the smoking group, which additional factor may be a contributor to the disease?

A) General environment
B) Brand of cigarettes smoked
C) The average age of each group
D) The duration of smoking