5887 middle age volunteers with asymptomatic airway obstruction from 10 clinical centers in the US and Canada underwent a 10 week smoking cessation program that included a strong physician message and 12 group sessions with behavior modification and nicotine gum plus ipratropium or a placebo inhaler (special intervention group) vs usual care participants (control). What would be an appropriate test to look at the effect of the special intervention on mortality due to lung disease, controlling for volunteer age, sex, and race? Break the situation down into the components for choosing a statistical test