A case-control study was done in order to estimate the interrelationships between different risk factors for the myocardial infarction (heart disease). Information on smoking status was gathered from a total of 791 cases and controls. Present cigarette smoking, explained as smoking within the past three months, was reported by 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 the current smoking and myocardial infarction.

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

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