The incidence of CHD in the exposed group (smokers) that is attributable to the exposure is calculated using Formula 12-1 :Formula 12-1
What does this mean? It means that 10.6 of the 28/1000 incident cases in smokers are attributable to the fact that these people smoke. Stated another way, if we had an effective smoking cessation campaign, we could hope to prevent 10.6 of the incident cases of CHD that smokers experience.
If we prefer, we can express this as a proportion. The proportion of the total incidence in the exposed group that is attributable to the exposure can be calculated by dividing Formula 12-1 by the incidence in the exposed group ( Formula 12-2 ):Formula 12-2