A case-control study was carried out to estimate the interrelationships between the different risk factors for the myocardial infarction (heart disease). Information on smoking status was gathered from a total of 791 cases and controls. Current cigarette smoking, described as smoking within the past three months, was reported by the 158 of the 367 cases and 111 of the 424 controls.

a) Set up the suitable two-by-two table and determine a measure of association between current smoking and myocardial infarction.

b) Determine a measure of the excess risk of myocardial infarction in cigarette smokers that is attributable to their smoking.

c) Specify any assumptions which you make in carrying out these calculations and provide interpretations for both calculations.