1. Twenty-seven cases of disease are observed in a population of 1000 persons. Of the cases, six victims are younger men, 8 are older men, 3 are younger women and 10 are older women. The population consists of 300 younger women, 200 older women, 400 younger men and 100 older men. Construct and interpret a control table of attack rates by age and gender.
2. Of 100 persons attending a UI alumni banquet, 40 develop food poisoning. Of 75 who recalled eating chicken, 35 fell ill. Of 40 who recalled eating roast beef, 32 fell ill. All 20 who recalled drinking milk fell ill. If you had no other information than this, which food would be first on your list of possible causes of this outbreak, and why?
3. An outbreak of salmonella poisoning occurs among patrons of a popular restaurant over a period of one and a half days. No one knows exactly how many people ate particular foods at the restaurant during that period and, since the symptoms range from minor to severe, no one knows how many people actually got sick. A sample of 100 known cases is questioned about what they ate at the restaurant during that period, and a sample of 200 people known to have eaten at the same restaurant during the same period without later falling ill is similarly questioned. Ninety of the cases and 160 of the controls had eaten at least one food containing mayonnaise, 85 of the cases and 80 of the controls had eaten soft boiled eggs, and 50 of the cases and 60 of the controls had eaten rare hamburgers. Which of these foods would be first on your list of possible causes of this outbreak?