Part I A cohort study followed 2,000 participants for 10 years to investigate the long-term effects of pesticide exposure (the exposure) on cognitive disorder (the outcome). Of the participants, 1,000 had been exposed to high levels of pesticide by virtue of their occupations and 1,000 had not been exposed to pesticide. The investigators also measured alcohol drinking as a potential confounder. The study had the following results for development of cognitive disorders after 10 years. Drinks Alcohol Non-alcohol drinker Exposed to Pesticide Unexposed to pesticide Exposed to Pesticide Unexposed to pesticide Cognitive Disorder 600 50 100 75 No Cognitive disorder 150 200 150 675 Total