Calculate the most appropriate measure of association and 95% CI and interpret the results.

1. The following hypothetical cohort data of 2,500 subjects observed swimming on the beaches of Ocean City, MD the last week of June, with baseline interviews conducted on the beach. The pollution level for each subject was based on average water quality counts from three samples on the date the subject was interviewed. Subjects were asked by telephone one week later to recall whether they had developed a cough, u or gastro-intestinal illness since the beach interview. Pollution level igh Lo_w Total 111 400 375 775 Not 111 600 1,125 1,725 Total 1,000 1,500 2,500